Larger vehicles will have some form of hybrid-diesel engines or powertrain.…
April 30, 2012 | National Geographic
Less than one third of the energy from the fuel put into the gas tank of a car with a typical spark-ignition engine is used to move the vehicle down the road. The rest is lost, mostly as exhaust heat, due to the engine's inherent inefficiencies.
Diesel engines, which use compression rather than an electric spark to ignite the fuel, are far more efficient, but researchers believe greater improvements are possible.