Can gasoline engines ever reach the efficiency of diesel engines?
Almost. It is indeed possible but not if the right things are done to both. A gas engine can be made to reach 30% Thermal Efficiency and a diesel can be persuaded to reach 40%. The trick to increase Thermal Efficiency is in stopping the wasted fuel and by reducing friction to nearly zero. Plus other things. The car companies will never do this unless they are ordered to do so by a tough congress.
