
What Determines Engine Fuel Efficiency: “Gas” Mileage of a Vehicle
Fuel efficiency is the product of two variables. Fuel density is one of two factors that determine fuel economy and thermal efficiency is the other. That is to say, fuel density and thermal efficiency determine the “gas” mileage of diesel, gasoline, biofuel, ethanol, and propane-powered vehicles

Why Diesel Engines are More Fuel Efficient than Gasoline Engines
Diesel engines are more fuel efficient than gasoline engines. That is to say, diesel engines get better “gas” mileage than comparably sized gasoline powered engines. There are two reasons why. First, diesel is a better fossil fuel than gasoline with respect to energy density. And second, diesel