diesel.Diesel engines tend to have better efficiency especially at less than full load.Gasoline/Petrol and LPG engines tend to have better power weight ratios.
A gas engine ignites gasoline in the piston chamber with a spark from a spark plug. The expanding gas then pushes the piston out and the motor moves forward. A diesel engine uses diesel fuel,...
No you would need to change out the whole engine. There are a lot of things a diesel engines has that gas engines don't. It is possible in theory, but in practice it would be so expensive a brand new...