[Racer]

If I recall there's rules for Ethanol , Methanol , Methane(?) , Petrohol etc in GURPS Road Atlases . Australia and Free Oil States ones spring to mind .
Also seen on NOVA pages I think , Hydrox Engines ( NOT Power Plants ) , that burn Hydrogen & Oxygen together instead of Gasoline/Petrol . Okay probably not available to the average Driver but an option none the less - also has the advantage of being able to run underwater .

Some vehicles in UK use LPG - Liquid Petroleum Gas - but that's an extreme rarity these days .