Petrol is now approaching 0.90 per litre. That's 4.10 a gallon. For every 50 fill-up, you're just giving the government 37 out of your own pocket. For the average family, a 1p increase per litre in the cost of fuel means an extra 46 a year out of their pocket. I drive miles a year.
Fuel duty has little to do with the environment.
Leaded petrol was supposedly taxed highly for environmental reasons. Diesel fuel, although potentially renewable by using vegetable oils, is no longer substantially cheaper than leaded petrol. LPG is the cleanest fuel there is but the government aren't actively trying to get you to convert. 36billion is sucked out of motorist's pockets each year in tax. No you do not.