In reply to Gordon Burgess-Parker:
I've used unleaded, benzin (so called white gasoline) and Coleman fuel. Coleman and white gas burn better and you can control the flame for simmering etc. With unleaded you have to have the stove running at full blast. It also has all sorts of additives which means it soots up something rotten. The Optimus site has a warning about using unleaded because of potential carcinogenic effects.
Any pure benzin will do the job and it is a damn sight cheaper than coleman - which you can't always get - eg. in Scandanavia.