UKC

Just filled my van with diesel. £130. Had to make two purchases as still a £99 limit.

What is your favourite fuel-saving trick? 

My dad used to recommend treating the pedals as if they were made of glass.

Only climb at shit crags.

Hello Trowbarrow!

Used to have quite a heavy right foot, but for the past fortnight I've been feathering the throttle, max 55mph, all on country roads. Made a huge difference - almost 100 extra miles per tank in the Caddy.

Buy a bike.

Regardless of what happens in Ukraine/Russia, fuel prices will never get back down to what they were. Every time there's a fuel crisis prices go up - but they never come back down 100% to where they were.

The cynic in me would suggest that's where the oil (I mean energy) companies make a lot of profit, but I'm not cynical enough to really believe that.

Pinocchio

I was interested to read that a car uses 50 times as much energy as an ebike.

And (if you are able to) work from home.

Agree there is a certain debate about the threshold of saving costs commuting -v- energy use at home instead (heat, lights, laptop, etc).

That's not really the case: it just depends on the crude oil price, and supply.There was a huge drop in crude oil price from 2014 to 2016 or so, and fuel prices reflected that. See e.g. the graph at https://www.racfoundation.org/data/uk-pump-prices-over-time

I recall that in 2016 the question being publicly asked was whether or not crude oil prices would ever recover.

Personally I am definitely planning my drives more carefully now. Everything is duel purpose. If I'm going to the gym, I will make sure to go to the supermarket on the way back even if I'm tired so I'm not making another separate trip. 

Other than that, just driving like a total granny. Easy enough to squeeze 5-10mpg more just by keeping it to 60mph on the dual carriage ways and only very lightly touching the accelerator. Basically attempt to never go over 2000 rpm. 

Sunak better cut fuel duty. He needs to do something ffs.. All well and good giving the poorest loans, grants, etc. But there's a big amount of middle class people feeling the squeeze too and if there's nothing for them, they'll tighten their belts and stop spending on luxuries and we saw what that did to the economy during COVID. 

Look ahead, think ahead, drive ahead.

But an e-bike is pretty shit for getting anywhere much.

I'm always amazed at the difference in mpg driving up the A9 from Perth to Drumochter and back again. A gradient of about 1 in 150.

The f*ck are you on about? What knackered the economy during covid was letting the virus spread everywhere until there was no choice but to shut *everything* for months and months on end to narrowly avoid the total meltdown of society as healthcare collapsed. The middle classes didn't tighten their belts, they didn't leave the house and what they'd normally spend on holidays and eating out they kept in the bank.

Look, we're in for a recession + inflation the likes of which people of my generation have no experience of. We don't know what's about to hit us, if the nukes don't get us first, or we're not conscripted. Rishi's not going to bail out the middle classes to keep us livin' the dream. We're saying goodbye to the living standards we're used to. The world's f*cked, and the UK is gonna be one of the first to go down.

That's what happens when you vote in the venal, gormless proxy of a fascist dictator. Everyone's f*cked now thanks to the idiocy of Tory Party and those who voted for them.

Years ago I discovered that Manchester to Carlisle always gave me better mpg than Carlisle to Manchester. I wondered whether different hill profiles in each direction (steep over less distance vs shallow over more distance - no idea which is better) made the difference because the difference in altitude over 180km was only about 60m, which didn't seem like enough to me, but maybe it was just that (average gradient 1:3000).

60m is not insignificant. Prevailing wind might also be at play but I'd guess if it was a journey you made regularly enough to quantify the difference there was probably some routine to it, maybe hitting different traffic each way?

Jk

Fracking and drill in the N S poles ?

the true cost of oil is not registered : yet. when it is, it will be self limiting in  extraction  .Then we will wake up to oil use  .

 Edit    Save weight on the car empty everything you possibly can don’t put more fuel than you need for your journey if it’s a long journey fill up  halfway. clean and polish the car for better air  resistance   Keep windows closed   inflate the tires hard. drive at night time driving in the very cool gives better engine efficiencies 

It helps if you take off the handbrake as well. :-}

Firstly, calm down. Take a few deep breaths. 

I'm talking about simple economic concepts like the UK being a consumer driven economy. When consumers stop consuming, shit hits the fan economically. That can either be government mandated, as with COVID, or simply practical limitations on how much people can spend because inflations made a litre of fuel £2 and a pack of 3 breasts chicken £10 and they can't afford anything more than the bare necessities to live.

The government needs to cut taxes temporarily. Inflation is being driven by higher energy costs, in part due to increased global demand for energy as we all come out of this COVID mess, and in part because of the Russia-Ukraine war. 

Odds are, in 2 years time fossil fuel production will have ramped back up to meet demand, and there will be some solution to the Russian-Ukraine war which will broadly be accepted by the world. 

So we need to do some targeted tax cuts, with fuel duty on petrol/diesel and VAT on gas/electricity being some prime candidates for cutting. Could even sunset clause them, so that the cuts expire in 2 years time. 

Shift this cost of living crisis onto the national debt, and keep the economy moving and people consuming. 

It'd weird, because the Tories generally love tax cuts. You'd think they'd be gagging for this, and yet they choose to squeeze the middle class from all angles.

The National Insurance rise is the shit cherry, on top of the shit cake.

The Tories aren't even good at being Tories.  

By jingo you've cracked it. Take a few pence off fuel and everything's going to be alright.

I don't know what I was getting so worked up about.

We need to acknowledge that our national debt has gone up phenomenally due to truly exceptional circumstances, i.e. the pandemic. We need to stop piling this debt onto the coming generations.

The Conservative government are spinning the lying dream. That is that they can somehow reduce the debt, but not increase taxes, and that they do not seem to have to note the effects of dramatically increasing inflation (and all the various sequelae that involves, including the self-perpetuating bit).

Mind you increasing inflation resets people's perceptions of what is normal for values of various items, and costs of living. It can effectively reduce the perception of how much someone owes in loans, as eventually the pay will increase, and after a long period the value of the loan becomes less, as a percentage of personal turnover.

This is the one increase in tax(effectively) which has been made. We will have to increase taxes. It just so happens that this one has not been fairly spread across the classes, and paid only by those who can readily afford the increase in tax on their income.

Don't drive unless you need to, when you do keep your speed down and be smooth. Anticipation is key.

I get an average of 34mpg out of my van (cost £144 to fill it yesterday. Its a 3.5 ton large van that I had on the weigh bridge last week. And the weight with a full tank and me in it was 3.2 ton.

My guys have the same vans but carry a fraction of the weight I do and average between 28 and 30 mpg, they don't pay the fuel bill. 

Now now Rog, call me a pedant if you wish, but its not a Van is it, its a Campervan and you dont have to drive it, so don't.
For walking and climbing, Wainwright did all walking by using the Bus, so thats possible, and cycle to the Supermarket.
Drive slower and smoother.

For me, and my Van, I will rationalise my work driving as much as possible, which will mean a poorer service, so some deliveries that would have been same or next day, will be 2 or 3 days.
Trips to Wales or Lakes will have to be at least 2 days of climbing, walking or cycling, and if the weather looks dodgy for the second day, I will not got, no more give it a go, see what happens.
Trips to Peak and Dales will have to be more than one in Van, so more sharing.
My cycling will be from home, I will have to learn to cycle up hills also I will be looking to use the Bus and Train more.
More local walking and climbing.
Drive slower and smoother.
Possibly these are things we should all have started doing 10 years ago, not because it hurts us in the pocket, but because it hurts the planet, and hurts people in the future and in distant lands.

Small rant, the bloke from Bury Council parked on a double yellow line for an hour, having his lunch, outside my warehouse, in full sun with your windows of your van open, did you really need to have your engine turned on for the full hour, to I assume keep the heater warm.

The law prohibits leaving the engine in a stationary vehicle idling unnecessarily. Did you complain at the time to this bloke? There's not much point complaining later on this forum.

Leicester to Woodbridge is very similar for us, about 200km and 80 metres of descent, usually a couple of mpg better going than returning. Most of the A14 is in cruise control so constant speed. But I think the wind probably makes the bigger difference, usually having a westerly component,  and it pays to knock a couple of mph off the cruise when going into the wind (cube law for aero drag). Regarding hill profile, short sharp climbs followed by long gentle descents are to be preferred - I always used to coast where possible, and in a motor-glider it is more efficient to climb and glide rather than power steadily along, giving better range. Current VW auto gearbox will coast in Eco mode but switching modes is more fuss than just knocking a manual out of gear so I don't tend to use it - and the benefit is hard to quantify in regular traffic. The extreme economy vehicles that minimise fuel use around a flat track use a brief burst of power and a prolonged coast with engine-off but they only have to average 15mph...

Is the journey REALLY necessary? Can it wait until tomorrow and combine several trips at the same time? Light on the throttle, avoid unnecessary revving, quick acceleration and breaking. Aim to be smooth, so think ahead all the time. Find out the car's most economical speed and try to cruise at that (obviously within legal speed limits). Car share if possible and subject to possible Covid risks. Use gravity as much as possible going downhill - no need to blip the throttle if the pace isn't quite as fast as I would really like. Always remove roof/cycle racks when not needed between trips, they increase drag enormously.

I am back on the bike commute! 

I think the fuel crisis might help keep my fitness up atleast. 

Cycled past diesel 179.9 this morning... Motivation to further increase my aerobic base. 

No. It took me a month to get a vacuous apology out of the council after a visit to my local recycling facility. 
It has taken me 4/5 months to get a Police officer to sort out a dog bite.
I am debating wether or not to continue my 5 month crusade to get a path opened, because the PROW officer is shit.
So please forgive me having a little rant and getting it off my chest, but some times, its just best to move on.

The point is presumably not to 'get an apology' - the point is to deal with the problem. If you'd pointed out the problem to the bloke in the van, he might well have turned the engine off.

Fair enough!

In reply to Shani:

You believe money is going to be cheap to borrow from now on?

I don't think in the same way, but when economists say that the Conservatives formulae don't add up, there has to be a serious look at the balance between input and borrowing and spending and debt. Plus the world economy is likely to get worse in the short to medium term, rather than better.

I suspect Jon is having a little rant because he despairs that the world will never be the better place that he would like (in his lifetime at least) because there are too many unreasonable f**kwits and bastards on the planet.

I had an amazing fuel saving measure once, car wouldn't go over 2000revs(turbo diesel), convinced it was a turbo problem, drove with window down listening, stopped it and started it again,  looked at fuses, pulled in a layby to pop the bonnet and gave the engine a good stare... limped to north wales (relatively speaking), then discovered the foot mat folded up under the pedal. 

A light right foot saves fuel! 

As others have suggested, I imagine strong winds will have a considerable effect on mpg. More so the bigger and less aerodynamic your vehicle may be. Even a 10 mph head wind makes a huge difference to energy expenditure on a push bike compared to a 10mph tailwind. I imagine a 20mph head/tail wind would make a significant difference to mpg in a car, even more in a Luton van.

Manchester - Carlisle is more likely to have a tail wind and the return a headwind.

My first Alhambra broke its fanbelt a couple of miles short of work one morning, no power steering or cooling but just managed to get there before boiling up. AA fitted a temporary belt and I pocketed a few big rubber bands as backup and needed them on the way home - but could not include the power steering pump. 50 mph max on the motorway and slow around any bend or corner because of the huge steering effort - and much better fuel economy. From then on drove much slower when commuting, it only takes a few minutes more and saves real money. Then I bought a motorbike...

Don't be ridiculous; we're climbers.

I got an electric car. I've not bought fuel since.

On a related note, extracting oil and refining it hasn't become that much more expensive, so maybe we should tax the higher profits in order to support people who will be pushed into fuel poverty?

Yup, ebikes are great. Have hills but don’t want to turn up to work exhausted and sweating like a pig? ✅ Have a cargo box on one and want to move a fridge/sofa? ✅ 

As for heating fuel, install maximum insulation that you can for your property, but be aware that condensation problems are likely to arise in areas of the dwelling which were not there before. Combatting this can be problematical because so much depends on the number of occupants and people's life styles. Increasing ventilation helps but that often directly conflicts with trying to heat the dwelling.

As climbers/mountaineers many of us have excellent well insulated outdoor clothing, so make use of it, particularly when sitting still, rather than cranking up the thermostat. 

It's false economy to stall our economy just because we're scared of debt. Spend in the bad times, save in the good time, is a general good rule of thumb. That's the basics of Keynesian economics, and COVID, and what we're experiencing now, kinda proved the theory right.. 

To give a household example, imagine you're a sole trader and you fall on hard times for some reason that is transient, and your revenue drops. You decide to cut back on advertising for your company, and you put off that new van purchase that will for 10 more miles per gallon. Now it's just compounding the problem. Now you get less jobs because you cut back on advertising, and each job costs a lot to get to because you're using an old van. Instead you could get a loan (deficit spending) and up advertising, and buy that new van (capital investment), and 2 years down the line be in a much better position financially than you would be by cutting back. 

I'm wary of giving household examples, because a country isn't a household and it plays by very different rules, but the basics are there. 

I think it's very strange that people were quite fine with tacking £400bn onto the national debt, and kamikazeing the economy into the ground to save economically inactive grandma, but we can't tack a bit more on for a few years to ease the cost of living crisis for young people who actually participate in the economy both as workers and consumers. 

You talk of wanting to protect future generations, but there doesn't seem to be any incentive at a government level to do that. The entire burden of this very costly saving grandma exercise over the past 2 years has been passed wholesale onto the young and economically active. The old, who by and large we did it for, are almost completely isolated from all the measures being planned to pay it back. 

So I don't think the government should be in 'tighten belts' mode just yet. Save that for when the economy is actually doing better. It's still in a precarious situation right now. Leaving the young (see: Taxpayers and consumers) to take on inflation, and tax rises, when the economy is already showing signs of floundering, and when we are relatively certain that these factors are temporary is very stupid imo. Especially when borrowing is still dirt cheap for the government. 

I think the current plan by the government, is incredibly unfair. 

Anyway, back to OP's question. For climbing trips I also now make sure the car is packed full of people for each trip to help share the burden of multi hundred mile drives I tend to do to crags. 

I keep hearing friends complaining about mortgage interest rates getting "so high" and thinking that they don't know what they're talking about.

Cruise control at 55. Did Andorra to Dover in one tank in a converted T5 with 195k miles on the clock that way.

When possible plan motorway journeys outside of Peak times. That will give less stop start driving, better for cruising.

I thought that cold air, driving in the morning comment above, was more dense and would have a negative effect on MPG. My 10 years of fuel /mpg stats suggest this. (older aircraft, in Africa, would prefer to take off in the morning as there was more lift)

They probably don't remember when mortgage rates rocketed up to 15% even 16%, IIRC in the 1970s. It was a very hard time with people getting into serious financial difficulty and repossessions becoming increasingly common. This led to a collapse in property values with an oversupply of property coming onto the market as people scrambled to off load their high mortgage commitments, and led to a lot of financial pain. I fear that we could well be heading that way again, with Putin's war resulting in human turmoil and misery throughout the world on top of the pandemic coupled with a major recession, possibly even a depression.

We may be heading for a significant period of belt tightening, the likes of which haven't been seen for centuries. It is becoming very serious indeed. It's hard to see a way out, but a start has to be ending Putin's war. I think even the Chinese are beginning to realise this.

Lift share. Going climbing? Join a local club and hook up with others to make the journey with a full car. Regular commute, get on lift share.com and find yourself a convenient lift share partner. Going into town, get the bus or get on your bike.

All that is required of you is a little flexibility and openness to human contact.

And whilst I'm on the subject try and make more time for yourself . Buses and cycling take a little longer but taking life at a slower pace means that you'll have a nicer life.

Yes I was being  ridiculous See below for  my view on the polishing cars from September11 2010  on UKC 

Regarding saving fuel I forgot to say that chipping The engine management system can make a large difference ask Volkswagen

User Profile Name Changed 34 11 Sep 2010

In reply to Franklin the pedantic cat: 

Yes , why polish a car ?  
Where’s the benefit,  
Where’s the loss,
Benefit help’s others to see that you are a sad looser who has nothing better to do than polish  

The loos in the recourses of a world running out of oil, not the car but the wax polish [ as if running a car is not bad enough!] 
The run off of the wax, the detergent to wash it before polishing, the water used, and the power to heat the water. 

It's the height of vanity to polish and parade, and a smack in the eye to those who look after the world, care and love it.

So a pleeee Don’t wash wax or polish.

Yes I have a car, wash it, no. Rinse windows and lights if yes, but hope the rain gets to it first, and if not its cold water , no detergent. 



From the fish, the rivers the sea’s and beyond, please don’t wash the car!

Could be wind direction -that can make quite a difference

then discovered the foot mat folded up under the pedal. 

glad it wasn’t under the brake pedal

Considering how indebted people are these days and the size of average mortgage (for people under about 40-45 anyway), if we see IR rise to those kind of levels again it would be carnage, mass defaulting.

We are in such a mess partly because IR have been so low for so long, inflating house prices for the last 20 years (along with other factors). 

As you say, worrying times.

Always look on the bright side of life, de dum de dum de dum

Certainly not the case in cars I’ve had. Current one, petrol, this week with warmer weather I am down 8-10% in consumption (based on in car computer); sometimes it’s been more and was last summer with the heat. Any cooler/wetter weather days and my consumption of petrol always goes up generally on the same roads (I say generally as it is impossible to replicate the likes of traffic, etc).

Can’t all be down to wipers, heater etc being on in cooler/cold weather.

Previous diesel cars were the same; always best consumption in warm dry weather.

 I may be wrong but my understanding was that cold air is better for performance hence the reason for intercoolers, nitrous oxide injection on sports cars 

 you’re looking at mpg (as topic) not the efficiencies of an internal combustion thick oil  heaters lights wipers blowers 

from google

The internal combustion engine runs on a mixture of vaporised petrol and air inducted from the atmosphere. Now, cold air is denser than warm air, so in cold weather the number oxygen molecules entering the combustion chamber per unit volume of air is significantly greater than when the temperature is high.

https://www.irishtimes.com/news/cars-perform-best-when-it-s-cold-and-damp-1...

Along with only driving when you really have to there are some tips here - https://www.rac.co.uk/drive/advice/how-to/fuel-saving-tips/

Dave

I tend to treat the 2000 rpm mark as a red line  (2.0 tdi)

This was old and smaller, but didn't need much more, just for passing dawdlers, otherwise yeah I'll spend 20 secs getting up to the speed of the road instead of 10. Once upto 50, 60, 70 everyone gets to their destination at the same time regardless of how fast their cars potential speed is. 

Yes your right as far as I know. Apologies, crossed lines I think.

Given you were replying to the OP which was about fuel saving trick though, I read it as you were suggesting that that cool condition was going to reduce his fuel consumption. My point was that over decades of driving that is not the case in practice for every car I’ve driven. Engines may well be more effective in cooler conditions for it’s own efficiency. I therefore missed (or probably misunderstood) your “better engine efficiencies” part, sorry.

I was actually aware that cold air will increase oxygen intake and makes the engine run more efficiently generally. That in practice though is generally about power output for same volume of fuel in test conditions as I understand it and not the day to day driving circumstances that a vehicle will encounter.

There is so much going on in the day to day running of vehicles that’s far different from testing conditions. I think modern cars are actually worse for consumption for the cold start phase than then older ones ime. They power so much more (last few cars have had auxiliary heaters and not just for the cabin, besides all the automated autonomous systems, and systems on by default using power) than older cars and this increases fuel consumption in my experience in practice.

Until the car fully warms up it won’t reach his highest designed efficiency and that is many miles (up to 11miles in my current car!) and it then has to try and offset the poorer mpg of the cold phase which in my experience is a distance much longer than the apparent average distance a (private) car drives at one time.

My knowledge has dwindled over the years as I’ve lost interest, but in practice ime cold weather driving increases my fuel consumption.

Buy an Audi. Then you are entitled to drive 20cm behind the car in front, thus slipping along in their wake.

Turn off the AC for a start. 55 mph maximum.

I agree, but you nearly get rammed off the road by hgvs wanting to do 56mph. 

The difference is that people now maxed themselves out with a rate of, let's say, 3% and a 5x joint salary multiple on a 25 year term.  A rise to 6% means a doubling in interest rate and huge rise in payments for them and no quick way out. Back in the 80's people were borrowing smaller salary multiples over shorter timescales and thus able to extend their payback terms if necessary.

There have been a few unscientific tests showing that there's no significant difference in fuel economy when comparing a car with A/C on or a car with the windows open. So if it's uncomfortably hot the the A/C wins.

Obviously there are a million variables that can't really have been considered in this loose study but it goes to show that A/C isn't the big issue it used to be.

I'd guess fast acceleration is the big fuel waster, and half the time if you accelerate hard in any form of traffic you'll be using the brakes a second or so later.

My plan is to use the bike more. I just need to encourage my nearest wall (The Depot Pudsey) to install some better cycle racks.

I'm pretty sure that coasting will make a substantial save in your fuel consumption.

As I understand it, it's not actually illegal and the advice not to do it stems from the notion that you are not properly in control of your car if your  engine and drivetrain is disconnected from the wheels. (It follows, then, that anyone not pedalling on a fixie is not in control of their pushbike all of the time. )

Of course, if you have an accident and it's deemed you weren't in control of the car you will get the book thrown at you, but that also applies to drinking a Starbucks , lighting a fag or using your infotainment screen to adjust the heating .

I wouldn't like it to become widespread advice for everyone because that would include the already incompetent but given that Saab used to incorporate a freewheel into their transmission systems  it can't be altogether bad. (I'm aware that the saab freewhel wan't coasting but the engine was disconnected from the wheels nevertheless)

For what it's worth, in my VW Jetta  with four  up on the way back over Woodhead I used to be able to coast  waaay past the Flouch crossroads in neutral. Given a good enough head of steam on the top of the pass, that is.

Get rid of the van. You don't buy one and expect it to be cheap to run ;p

I'm kidding, of course, before I get flamed

Mine is to drop the speed and bit and set off earlier, and if the roads are quiet enough, cruise control as much as possible, including using it accelerate and decelerate where safe. 

Been averaging 50-51mpg from a 2010 Honda Civic Type-S on longer runs, which I think is pretty amazing for a 1.8 petrol that will go absolutely bananas if you do decide to put your foot down.

I'm convinced by my own mediocre -- though painfully scrupulous -- experiments commuting that it's the rush/go-then-brake of urban driving that kills fuel economy. That and driving faster than 60mph on duel-carriageways and motorways. What speed do diesel injectors start at, or is it based on revs? Motorway 70 seems much worse economically than 60, and when speed restricted to 50 it gets even better in a 2.0 diesel estate.

In a modern vehicle coasting down hill (in neutral or clutch depressed) actually consumes more fuel than if in a high gear because the engine uses fuel to keep it ticking over. If the wheels are effective turning the engine because you are rolling down hill in gear the ECU doesn't fire the injectors so no fuel is used.

I have a bar graph display on my dash showing fuel consumption. At 70mph on the motorway on an incline, using cruise control, the engine revs increase to maintain 70mph and the fuel consumption increases by usually 10mpg less for the duration of the incline. Without using cruise I subconsciously keep the pedal in the same position and slow down by about 5mph.This keeps the fuel consumption at a steady low. Also, using cruise to accelerate is like putting your foot to the floor.

This is not the only reason I never use cruise, I think it is quite dangerous on our busy motorways except perhaps late at night.

Almost correct, but the engine applies a braking load when no fuel is injected which usually outweighs the small amount of fuel consumed to maintain idling. Sometimes this retarding force is useful, if the incline is causing speed to increase too much. You have to be prepared to slip back into gear if this happens and you can then save a little bit more fuel (and avoid some braking - brakes are the main reason fuel gets wasted!)

This depends what engine you have. Small petrol engines give very little resistance and some engines even lift the valves slightly to reduce this.

Cold air is denser.  That's bad for fuel efficiency because it makes aerodynamic drag more significant.  This is much more noticeable in an EV (which do almost all of their work against drag) than in an ICE (which only do about 30% of their work against drag, dumping most of the rest out of the tailpipe as hot gas).

However, it will increase the engines maximum power output.  Roughly speaking, to get max power from an engine you need to get more oxygen in per stroke.  You can always inject more petrol so oxygen is the limiting factor (well, that or the ability to get exhaust gases out fast enough).  Cold air has more oxygen per volume so you get more power.  This is also why a turbocharger or supercharger (ways to compress the air before pushing it in under pressure) will help.

So you may well find your acceleration is better in the cold, but not your economy.

How hard you accelerate has surprisingly little effect upon economy.  You burn more fuel, but you also gain speed faster.  You end up with the same kinetic energy.  There will be differences in how the particular engine performs when being pushed harder, but not that much.

It's the brake pedal that's your enemy, not the accelerator.  Every time you touch the brake* you are turning hard won KE into heat in your pads and discs.

* assuming you don't have some recovery system like an EV regenerating to the battery.

So, to be clear, rolling down a hill in 6th gear uses no fuel at all?

If that's the case ( which it seems to be) what happens on steeper hills in lower gears? 

Walk journeys of less than 2 miles. These add up to more than you think, are your most inefficient miles and unless the weather is really grim, it’s quite enjoyable.

even combining journeys, we never just shop, but always do it coming or going from elsewhere, it saves time too. 

Buying two lots of rationed diesel is hardly fuel saving.

In lower gears you do use slightly energy to spin the engine and gearbox so you may slow down the vehicle but whether that is significant depends on whether or not you would otherwise be using the brakes to control your speed or if you want to get to the bottom of the hill and continue going quickly.

While there's no load on the engine you won't be burning petrol.

My girlfriend's car is quite good for demonstrating this as it has an issue with clicking injectors so you know when you're using fuel. Fingers crossed they don't pack in though as they would cost more that a few tanks of petrol to replace, even at the current fuel prices.

Our car is pretty good for showing this, as there's a live mpg gauge on it. Going down a step enough hill in gear can get the fuel consumption to zero. If I put my foot on the clutch, then it goes up as it injects fuel to keep the engine running. 

With regards to gearing on hills, there's a 40 mph hill near me which I have tried this out on. Using 6th gear uses a small amount of fuel, whereas using 5th uses none. I understand this is because the ECU will not inject fuel if the engine is being driven by the wheels... so long as it is at least at idling speed (for me about 1000rpm). If I roll down a hill in a gear that's too high, then the engine won't be driven at >1000rpm, so it injects fuel to reach this. 

My previous Golf 2.0 diesel showed this well - coasting out of gear gave 300mpg, in gear infinite mpg (but with a retarding effect). I was happy with 300mpg, not sure you should be encouraging the engine to run slower than idle even for demonstration purposes...

Thanks for that.

No problem!

In reply to petemeads:

If coasting downhill in top gear has a retarding effect, then it must be spinning the engine faster than idle.  If it was running the engine slower than idle then it would continue to inject fuel to try to bring it back up to idle speed.

Firstly, that's not how I drive, if I'm doing 70 I will maintain 70 with my foot even on a hill, so no savings there. Secondly. and far more importantly, consistently maintaining a speed that's considerably less than other vehicles of the same class on the motorway saves a hell of a lot more fuel than not slowing down even further going uphill, and maintaining that speed is far easier than having a right foot itching to get up to national.

Which is why it's preferable to accelerate with your foot and then set it at that speed.

Because...?

Most of that comes from the time of carbyrators. Fuel injected vehicles inject no fuel if there is no load. Maintaining idle is a load, the engine being driven is not.

70 odd posts in and nobody has mentioned tyre pressure...

You are overlooking efficiency. The average efficiency of an ICE is 18-20 percent. This inefficiency is cause by friction in the engine amongst other causes. So thrashing the engine does reduce the efficiency dramatically as there are about 3 times as much revolutions of the pistons. 

ICE's are truly crap. There really isn't anything you can do to mitigate the costs in a van. The  drag cube velocity isn't tractable because shitty vans don't go over 60mph anyway. The drag coefficient effect  is linear with velocity but really there isn't much you can do to reduce that other than buying a car.  The OP will either have to suck it up or sell the van and buy an electric car or a bike.

Good point

I did

I agree coasting does make a difference.  But I think E10 petrol has increased my consumption from 68mpg to 65mpg.

It isn’t rationed -yet! And fuel saving is about how you burn it, not how you buy it.

Name Changed 34 mentioned it in https://www.ukclimbing.com/forums/off_belay/saving_fuel-745290?v=1#x9607659

Just to be the pedant for a moment - I think mpg is measure of fuel economy. Consumption is gallons per 100miles or other unit of distance.

on another point, I’m interested in the effect of transmission type. Our van has an automatic gearbox but you can switch to manual mode in a moment. My better half likes the auto, and I prefer the manual, if only because in auto mode it is very reluctant to move up a notch and this means it’s spending longer in lower and noisier and ?thirstier?  ratios. We’re advised to get into and stay in higher gears as much as possible to save fuel. How much extra fuel does an automatic use? Apart from the above, why? Is a clutch more efficient than fluid drive?

Going up hill, does there come a point where changing down is more fuel efficient than staying in a higher ratio?
So many things to confuse one.
 

1. Don’t use the car. It uses no fuel parked up 

2. Do not use the brakes. This is THE most significant driving measure you can take. It’s not the actual braking because that is only converting to heat the kinetic energy of the car that has been achieved from fuel already burnt. You have already wasted that fuel before you touch the brake pedal. The key thing in not using the brakes is that it compels you to look and plan ahead, regards road conditions, hills and bends, so as not to put in excess energy with the right foot only to scrub it off again soon after.  

Many folk also  brake unnecessarily without thought and by habit. Braking at every bend or in response to a perceived hazard.

As previously stated an engine uses no fuel in overrun so coasting out of gear is counter productive. Additionally it is terrible driving, dangerous.

Lastly if driving a car on a busy flowing dual carriageway or motorway you really should be doing at least 60 mph, ideally more.

56 mph is the heavy truck zone and cars have no place down there. It’s how it is. Saving a few quid on fuel is no consolation sandwiched between two 44 ton trucks in a pile up. Coaches are limited to 62 mph and cannot use the outside lane so don’t be blocking them either please people

There is such a wild variety of different automatic transmission types these days that it's impossible to answer that generically, it depends on the actual transmission. For example I doubt an AMT would have any appreciable difference in fuel consumption, since it is just a manual transmission being driven automatically.

Weight would be a major reason I would imagine.

Thanks for putting me right, sorry Name Changed 34.

Damned, I read the thread and searched for "tyres".  Damned you, creeping americanisation.

According to an energy consultant quoted in a fairly bleak article on energy in The Sunday Times last weekend “If Russian oil is not integrated back into the market within the next few weeks, we are at a real real risk of having to ration crude and products by the summer” and that diesel rationing could start as soon as April! 

Very much agree with you up to the point where you seem to have failed to take on board the subtly different coasting scenarios - overrun uses no fuel, agreed, but it does slow the car down. Traditional out-of-gear coasting even allows the car to speed up but there is the tiny cost of the idling fuel to balance against this - on long gentle descents it wins hands-down. The highway code warns against coasting but it is not forbidden. My Golf coasts in Eco mode, try telling VW that this is dangerous, and even when I used to select neutral in my manual cars I was paying more attention to the road, and anticipating, than most regular drivers I believe. I used to fly gliders, I suppose that must be dangerous as well...

Fair enough, to a point. The potential savings are minute and inconsequential against the key technique  of avoiding use of the brakes. Each to their own but I personally would never coast out of gear as I do not believe it gives full and proper control, that has to come before fuel saving. This is no doubt a personal perspective dictated by background, including driving trucks and buses which are automated manuals not automatics. I would never coast them out of gear. I’m afraid I don’t consider the different coasting scenarios as personally it is something I would never do.

I said surprisingly little, not none.  There will be an economy gain to be made from accelerating smoothly and gently, but not all that much.  And there will be gains from changing into higher gears sooner (at perhaps 4500rpm, not 6000rpm) because of reducing the amount of internal friction as the engine cycles, but again not all that much.  That friction is only one of the many things the car is working against.

Hugely more significant is the difference between a driver who is anticipating the road ahead, easing off, and never touching their brakes, and the driver who comes up to an obstacle and brakes, before accelerating again.

If we consider three drivers https://photos.app.goo.gl/CKFGNQEaXNMzwhch9 doing the same journey in the same car, but A accelerates up to top speed slowly and B accelerates to the same top speed quickly, then B will obviously arrive a little sooner than A.  I'm suggesting their fuel consumption will be very similar, though; their losses against exhaust gas heat, aerodynamic drag, road friction will be more or less the same - only very slightly higher because they spent more time at a higher speed.  They'll have had a slightly higher radiative loss from the engine when it was hotter during the acceleration phase, and slightly more friction when the engine was spinning faster (assuming they are changing up a little later) but these are small.

C, who keeps running up to the car in front and braking and then accelerating again, will burn lots more fuel because they keep losing KE as brake disc heat.

It all that were true then the engine efficiency would be >18 %.The car and road isn't the engine. ICEs have many forms of loss and the harder you drive them the more you loose and over time the losses just increase. They use oil because they are naturally sticky and frictionful 

Electric motors don't need oil and they go on and on without significantly loosing efficiency. The efficiency of such a motor is 75.%. 

Modern turbodiesels are well over 30% efficient,  fast acceleration does not rely on high revs as max torque is below 2,000 rpm usually. Your electric motor at 75% uses electricity generated and transmitted at around 50% efficiency so not that much better.

EVs have the advantage of charging whilst coasting and braking, our hybrid even when fully loaded inside, plus a roof box, on a long drive averages under 6l/100km, lose the box and it's under 5l, I'll never go back to a purely ICE, if anything it's full EV next. 

One of ours running on gas gets 91% efficiency, it's useful if you can use the heat produced! 40% is good just for the mechanical energy available nowadays. Typical generation plants run around 40-55%.

Yes and I'd add into that the 17%efficiency of solar panels and some very low efficiency of windmills but what we are talking about is the cost of motoring. So it's cost efficiency really and as those sources of electricity are about 25% of that of hydrocarbons per mile then  electric cars are actually 300% efficient wrt hydrocarbon cost per mile. Don't get me started on climate damage.

Perhaps I assumed that the garage rationed petrol.  Or is there another reason for the £99 limit.

I'm afraid I'm struggling to follow your argument.  Are we talking about ICE vs EV here (I'm sure you know I am pro EV), or the effect of different acceleration styles on an ICE?

Interesting thread, reminds me of an idea I had for intelligent cruise control.  Roads are now well mapped, including corners and inclines, has anybody used this data to develop a system that balances journey time and fuel consumption?

e.g. if a corner is coming up that would require braking, the cruise control backs off the throttle well ahead of the corner and allows the car to slow down naturally, minimising loss of energy to the brakes.

This would fit in pretty neatly with self driving systems that are coming, but I'm guessing it would be significantly simpler to implement than self driving as there's no need for dynamic awareness, just comparison of current position with static map data.

On a modern car DON'T coast downhill, instead stay in gear.  If coasting, a small amount of fuel is used to keep the engine idling.  If you stay in gear, the wheels turn the engine so the fuel input is off completely and none is used at all.

That will be cool. All those old grannies going round corners at the computer-optimised maximum speed!

A few heart attacks may ensue!

That's simply not true is it, this link doesn't even take inflation in to account! https://www.racfoundation.org/data/uk-pump-prices-over-time

Inflation adjusted we are currently around the same price as the 2012 peak

That’s an ace crag!!

Slowing down is slowing down. The point of avoiding braking is to not have to constantly change speed, which uses up energy. Whether you ease off to get to the right speed to take a corner or whether you brake, you will drop speed and then need to accelerate back up, it doesn't matter whether the kinetic energy is dissipated on the brake discs or compressing air in the engine.

don't build up momentum you can't use or lose slowly.  Conserve momentum where possible while negotiating non linear features

Use gravity to gain momentum where it will exceed losses

build and conserve momentum to go up hill to avoid lower gears

without turning engine off and locking steering

Nailed it - thanks!

For several years now if you buy fuel at many supermarkets you can only pay by card and the self service pumps are programmed to limit you to £99. I don’t know, but it isn’t rationing.

aided by the stability control saving them 

No, The point is that if you just take your foot of the accelerator and let the car decelerate to a corner without braking, over , say, 10 seconds, you use the accelerator for less time than if you keep your foot on it for longer and then use the brake over, say, 5 seconds. Less braking means less accelerator and therefore less fuel used.

Thanks. I didn't know that.   I obviously never buy that much fuel !!!

Yes, I'm the same. I'd hate it if someone stole my car with £100 quidsworth in the tank.....

The way things are going, you won't have much choice soon!

I've lived in France for 10 years where this is the norm everywhere. On a recent trip back to the UK I was genuinely shocked that the UK hasn't caught up and I had to physically go in and pay for my fuel. 

100€ limit on many pumps here. Filled one car up to 94€ the other day and a few weeks ago my Passat (which has a much bigger tank) was 104€. Dread to think what it will cost next time. 

I should be ditching both in a couple of weeks taking advantage of the government grants and going fully electric and since COVID we're both traveling less for work so will make do with one car. 

One thing this thread shows its that as soon as prices get high people look for ways to save fuel, usually to save money. This means surely things like the fuel escalator and high duty are effective measures to get people to reduce their fuel use and therefore carbon emissions. 

When the gillets jaunes movement started in France it was primarily about high fuel costs, but I always used to see people in cars supporting the movement with a yellow vest on their dashboard tearing around 90kph roads at 110, braking and furiously overtaking and therefore using a load more fuel than they needed to. 

You have articulated a lot of things that buzz around my mind. Your last para has a wider applicability.

Not sure why the limit on purchase is there. Anyone know?

……. yet.

There were still pay in service station options on a recent drive across France on the toll roads.  I wonder whether as the UK petrol retailers often have a tie up with a supermarket chain they want to encourage a visit, or perhaps there is more “bilking” on the continent!

Yes but they pretty much always have the option to pay with your card at the pump. 

Supermarkets often have a little booth you can pay at after filling up but I rarely ever notice it open. 

Agree with you here. It is problematic though.

I know a chap who is very right wing and bangs on to me about how we have this huge debt which is growing and therefore we can’t afford the NHS, or schools or piling money into the “vast numbers of refugees coming over here”. I point out that therefore we should tax the rich more and he responds with the “Well they’ve worked hard for it so they shouldn’t have to pay” argument I also pointed out that the biggest expense was on older people and pensioners (like what he is and me if it comes to that) so was he in favour of dropping pensions? To which he responds that he’s already paid for his pension (which technically he hasn’t as that is being paid for by the current generation.) Oh and he also says that there was no austerity because the left scuppered it. I am constantly amazed how after twenty odd years of tory rule (and more if you think that Blair basically nicked Thatcher’s policies) that someone can still say we are in the shit because of the left.

BUT that aside yes there is a whopping great national debt (Though percentage wise not as large as the one left after the second world war when you allow for inflation.) And I agree with you that you can’t just get ride of it by cutting services to nothing as that is a downward spiral. An aging population means that there is increasingly going to be a problem with the elderly none contributing population. Unfortunately those young people suffering now will themselves be old some day and if they haven’t built up savings will be more dependant on the state than those who are currently dependant. Again a downward spiral.

To me this is the result of years of cutting taxes, allowing tax avoidance loop holes to syphon off money from the system etc. If we went down the Logan’s run route may be we could sort it out.

Something similar from a driving instructor decades ago assessing students wanting to drive union minibuses. Only stand on the pedals as hard as you would if one of your testicles was between your shoe and the pedal.

Brings a whole new level of severity to an emergency stop.

In reply to Shani:

Ooo now that is an interesting statistic to throw at those who say labour borrows too much.

Gotta a source I can use?

If one of your testicles is between your shoe and the pedal, you probably have more important things to worry about than fuel economy.

It boils down to 'work done'.  going from A to B requires the same amount of work (energy / fuel consumed) irrespective of speed bar the following things:-

1) air resistance - increases as the cube of the speed

2) engine efficiency at different RPMs - an engine will have better efficiency at differing RPMs

3) engine efficiency at different throttle settings

4) gearbox efficiency - efficiency varies depending on which gear you're in.

Obviously all those things have different values, but I suspect the most efficient behaviour is something like the lowest speed in the highest gear reached using the most efficient amount of throttle and the most efficient rev ranges. The length of run will also be a factor in terms of balancing the gain from spending longer at the most efficient speed versus the most efficient way to gain that speed.

I have been noticing slower speeds on the motorways, my cruise control in my van is normally set at 65 mph (60 actual speed) and I have definitely notices less people overtaking me.

Those that do are mostly I would estimate doing about 70.

Sign written vans are still hooning along in the most part but most of them are driven employees who don't pay the fuel bills. 

Square of speed in terms of work done over the journey, cube of speed in terms of power during the journey.

Goes up with a crosswind or a headwind, goes down with a tailwind.  

Unless I am misunderstanding you, you aren't accounting for the additional work being done in heating up and eroding brake pads and tires in the example of the person who is unnecessarily accelerating and braking more heavily. 

Just done Manchester to Anglesey but maxing at 70/71 rather than my more normal 75 (on the speedo). Got 65mpg, don't think I've ever got more than 60 on a long run before. Just those few miles per hour makes a significant economy.

Keeping my van around 60 rather than 70 takes it from 28 to 35 mpg. When you drive 600 to 700 miles a week that's a good saving. Okay it takes a bit longer but its only a few minutes a day. 

Fuel economy of my van has typically been between 29 and 30 mpg for a journey like yesterday’s from Kendal to near Evesham. On motorway that is driving at 65 - 70 on the clock. Yesterday set the cruise at 60, which for much of the journey on smart motoway is the maximum anyway. It helps when more other drivers are doing the same as less use of both pedals. The computer was showing an average economy of between 34.5 and 35.5. Although these figures are poor compared with a car, this is still a very considerable improvement, around 16 - 18% if my quick mental arithmetic is anywhere near right.

it just set me wondering with present world problems how long it will be before we have a 50 mph limit universally to both save fuel and reduce CO2. 

1) air resistance - quasi linear at low velocity, proportional to square of velocity at high velocities. The boundary between the two is defined by the Reynolds number.

Drove from Glasgow to London last month, set the cruise control for 72 instead of the usual 75 with regular bursts of 80+.  The car’s computer said 67 mpg, brimming the tank showed a real 62 mpg (in a 3 series) - compared to a normal 53 -54 mpg on my usual long runs. Definitely worth easing back the pace a bit.

We have an oil fired boiler in an out building in it's own closed off section. We use this as a boot room. No windows and just an access door. Realised this room is always warm, so I fitted a long wardrobe rail along the length of the room hanging from the ceiling and use this to dry our laundry rather than tumble drier. Definitely saved a few quid on the electricity bill.

There is a restricted 60 zone on the M1 between Barnsley and Sheffield to reduce emissions. 

I have just driven from Stirling to Bristol, I have been driving at about 55mph, behind lorries. A safe distance behind but as close as I can get whilst still being safe. And I've been very gentle on the throttle. Lookig forward and coastin- before braking.

Usually my fuel light comes on at 360 miles. Today I got to 380 miles with half a tank left! I've saved myself £80 by boring myself to death. Winner! 

The m27 is also restricted to 60mph, either as an emissions measure or as a late recognition that removing the hard shoulder was a dumb arsed idea and now motorway speeds are too dangerous. 

Use a bike wherever possible! 

- I take/collect my 2 children to nursery/school on 2.5 mile round trip using a bike trailer (which is actually faster than by car as it avoids the school drop off scrum) - takes 22 minutes assuming no-one is chin-wagging with the nursery staff.

- I WFH now mainly but manage the 40 mile round trip to the office with my laptop in a pannier. This isnt faster than by car but is faster than the sum of car + separate form of exercise

Apparently though this type of approach is "impossible" according to a seeming majority on the local facebook group who cannot countenance any approach that doesnt involve motorising themselves around.

By using bikes for local journeys it means a little less stress about the extra cost of fuel for longer journeys.

However, it may have been a false economy as our car (Skoda Superb) had its coolant pump seize up recently at a replacement cost of £600 - apparently something that is accordingly to the garage becoming increasingly common in cars that spend most of their life sat idle on driveways.

Top tip, drive less.

It’s not an either/or question.

Latest stat: drove from Bridgwater to Kendal two days ago. CC set to 60 on the speedo. Fuel economy (normally 29-30) clocked 37.5 for the whole journey. Quite impressive and we’re not in a hurry. Once you get into it and stop being competitive with other vehicles it all feels quite relaxed. Mind you, there were no significant traffic delays.

I also sense more people slowing down a bit on Mways. Most of the people going eyeballs out in vans are commercial vehicles where drivers aren’t paying the bills and where time is money.

Yes, I do that, as long as they’re doing the required 85mph.

I once saw some chap on a (presumably very high-geared) push bike slip-streaming a double decker bus at 40mph down the Kingston by-pass. No effort required in the sweet spot at about 2 metres. Impressive.

Will have to try that.  I do find it easier to drive on cruise control with a decent speed differential to other traffic so you're not doing lorry style long overtakes for 1mph difference, so 60mph might be more enjoyable, too.  Actual 60 (so set to about 63-65) might be better so as to be faster than lorries (56) but slower than coaches (62) so you're not stuck in amongst large vehicles for long periods.

I found that if I got about ten to fifteen feet behind an eighteen-wheeler truck in my Toyota Prius in the US, doing 70 mph, I could get about 100 mpg. But I only tried this for a few short periods, because it was very bad driving practice: I was a mere fraction of the safe driving distance from the truck.

It's probably the best part of 25 years since I slowed down and the first thing I noticed was a big drop in my stress levels. 

Time is money in my world but the fuel saving as well as general wear on the van is worth more than the couple of minutes saved on a 60 mile trip. Like you say though, most are not paying for the fuel so they don't care. 

During the great fuel panic last year I was forced into slipstreaming trucks to make a drive from London to Sheffield. If works and you can feel it happen and ease off the accelerator. But it only really works with HGVs and when you are so insanely close, I mean really really really close like a single cars length at 60mph. You have to be white knuckle on steering wheel eyes wide, and nervous exhaustion on arrival

My advice is do NOT repeat this, just don't do it no matter what fuel costs. Don't entertain any slipstreaming suggestions 

Slip-streaming a lorry or similar, may improve your fuel consumption, but it also could save you time.... on your life. If you suck in enough carcinogens, and other factors in their exhaust that affect your circulation, you may end up with a time saving on the length of your life. More so if you end up in the back of the vehicle that you are following, as said above.

Tailgating trucks.

… is a mugs game

I had to do a drive up from just outside London to the lakes (okay I didnt have to but fk it that was my first proper holiday in the year so.....) on the Sunday everyone started panicking.

Even not slip streaming a truck the cutting speed back and cruising at 60 or so gave a insane increase in fuel efficiency. I was surprised when my miles to zero indicator kept moving up despite being a 100m or so into the drive as it adjusted from my normal driving style.

Maybe I'm missing something but I assume that those drivers who sit with their engines idling (taxi drivers in Fort William & parents waiting for kids at Inverness leisure) don't pay for their fuel.. 

I'll bet the taxi drivers will be amongst the 1st to moan about the cost of fuel.

Such drivers are environmentally damning and also damned.

There was an article in a recent Guardian about Highmilers (which of course reminded me of something else). It seems a highmiler is someone obsessed with car fuel economy. I’m trying not to become one. Apparently one of the top experts can get 100 mpg from some diesel car he drives.

Stationary idling is an offence. If you are concerned about it, you then the obvious thing to do is to (politely) challenge anybody who you see doing it. It's better than moaning on here - and maybe the people involved simply aren't thinking about what they're doing.

You wouldn’t need to be the brain of Britain to work that out. Compare the average bike battery rating to a Tesla. And a car can take 5 people plus luggage. Trip down to the Alps with all the gear on an e bike anyone? Best of all hitch hike like we used to and use someone else’s carbon footprint.

I filled up this morning, 669 miles for 73 lts of diesel or 40 mpg. That's a new personal best.

For this last tank I dropped from my normal 60 to 65 mph to 55 to 60 mph and a few times I did do 70 mph.

That's an extra 6 mpg for a 5 mpg drop. 

I drove like a granny and got 122 miles by the time the first bar dropped on my fuel gauge on my van. 

I drove normally, not stressing so much about trying to be fuel efficient, and got to 117 miles by the time the first bar dropped on my fuel gauge. 

Conclusion: Not worth the incredibly boring driving, and all the extra concentration I have to do. 

I will stick to 55-60mph on long motorway journeys, because I think that likely does have a big impact on multiple hundred mile journeys. But other than that, I'm going to stop stressing.