Why do vehicles get more mpg from diesel than petrol?

Question

i need to do a presentation on this in my chemistry class i know how the different engines work and that diesel has a higher bpt and density because it has longer chain hydrocarbons but i still don't seem to have answered the question any help please

Answer 1

It has to do with the efficiency of conversion of the hydrocarbon. Gasoline is mixed with air and compressed and then sparked to create the chemical reaction that gives off the gases that expand to drive the piston. Diesel fuel is also mixed with air (usually turbo driven) and compressed until the mixture explodes (aided by a glow plug). The compression is higher and the fuel more efficiently converted even if it does appear to pollute more because of carbon emissions. Also diesels use larger cylinders which give economy of scale.

Answer 2

larger hydrocarbon chains have more energy and diesel engines are more efficient