does diesel give better fuel economy than petrol
Report Abuse. The reason diesels give better mileage is that less of the energy in the fuel is turned into heat which has to be got rid of via its cooling system,it revs a lot slower and the fuel can be metered a lot more accurately as it does not have to be mixed with air before it injected into the combustion chamber.o, you get more mechanical work from equal amount of fuel. Diesel engine gets more power from the same amount of fuel than it petrol counterpart. It means you have better mileage. Their notorious loudness is not an issue any more, modern diesels are almost equally quiet as petrol cars.