Maybe petrol should be charged based on engine size?
If you have an 8.0L V10 it should be more or less free as you pay higher road tax, if you have 0.9L 3 pot Fiat, it should be ?2 a litre as they get free road tax!
Seriously though, I agree with ZS about removing the Road tax if they are going to charge ?1.30 a litre. I only do 8000 miles a year yet pay the same as a business user doing 80000.....