Fuel for transport use is taxed more heavily in the rich world than fuel for heating or electricity. According to a new report from the OECD, a think-tank, the effective tax rate on energy for transport use is $15 per gigajoule compared with only $1.20 for other fuels. In the average OECD country transport accounts for 23% of total energy use and 27% of emissions, however it make up some 85% of total excise tax revenue from energy products. Effective tax rates on transport fuels vary both within the OECD and by fuel type. On average diesel is taxed at a lower rate than petrol. Litre for litre diesel has around 10% more combustion energy content than petrol, but it also produces some 18% more CO2 emissions than petrol.
source: The Economist