UKC

So, after finally acting on various recall notices (the bombs could detonate at any time) I took my car to the dealership to let them fix it. They weren't impressed by the dents, scratches and gaffer tape, but heigh ho.

Here's the question: before, a full tank read mid 390 miles on the range display. Since, it reads mid 360s. I've not noticed a reduction in how far I can get on a tank. Any ideas? I'm curious. 

No actual knowledge here, but presumably they've updated your onboard software or firmware and the later version has a modified algorithm for estimating range.

Have you altered the way you drive it just prior to filling?

I've noticed my range is all over the place once filled and presumed it was reflecting how the car had been driven in the hours before filling. 

Is is a diesel that needed a firmware fix to undo the emissions fiddle?

To all,

No change in driving; petrol car. I'd personally considered a software update - probably the most likely. Dunno why they'd bother on my old banger though. Thanks everyone. 

Basically the software takes your recent driving style into account when calculating predicted mileage.  The dealership therefore must have ragged the sh** out of your car when they had it.  I am sure a few weeks of careful driving will see the figure increase again.

They’ve upped the percentage of ethanol in regular fuel since you last had the software updated

Nice theory, but it's one of the only two Toyotas that theoretically mustn't have the new stuff, so... (And of course it gets filled with the new stuff.) 

What were the recalls?

Assuming it wasn't a tank sender change It'll boil down to one of three things, possibly a combination:

The firmware was updated meaning range is calculated differently.

Your fuel consumption has changed through a fault or a chang in recent use/driving style, the computer has logged this and fed it into the range calculation.

It's responding to environmental conditions. Likely high air temperatures, possibly because you have your air-con on (arguably that comes under recent changed use).

jk

Is it a Yaris GR or something?

The airbags could have potentially exploded without warning. No change in driving style, and it's never varied in the past.

Guffers: it's an Avensis. 

Try the aircon, maybe you don't normally use it but the garage turned it on.

Is it possible you didn't brim it for some reason? 365 down from 395mi is a ~7.5% change, that's roughly 4.5L. A slightly sloped forecourt or rushed fill could easily account for it.

Hotter weather makes the fuel less dense (~1% for +10degC, smaller than that in reality as the tank also grows) and the engine less efficient (~4% for +10degC). It could be your computer factors that into its prediction, that would get you most of the way to your 'loss' on a hot day.

Both of my range indicators (EV and diesel) vary enormously, easily +-10% with relatively small changes to my driving/use/load/conditions.

If you're sure it really been changed you could just call the garage and ask why.

jk

Indeed, the expansion and contraction of fuel Is considerable, for petrol 1% for every 8°. The fuel delivery companies, the fuel pumps and hopefully the ECU knows this, they use a temperature sensor to revert the amount to what is termed V15 (the standard volumatric temperature. One doubts the  average car tank level sensor knows this! One of my toys has to be re-jetted for both air temperature and fuel temperature (naturally air pressure and humidity as well), one hopes any modern car also does this!