an automobile engine runs on liquid air and gasoline . the liquid air is initially pumped up to a high pressure such as 200 atmospheres and is then warmed toward the ambient temperature in a heat exchange and changes to the gaseous state . subsequently , it is permitted to expand , doing useful work on a piston or other known type of expansion engine . the gas is then passed through an additional heat exchanger where heat is absorbed from the ambient , and is combined with a small amount of fuel such as gasoline . the gasoline is ignited , under constant volume conditions thereby bringing the pressure back up to approximately 200 bars and at a temperature in the order of 1200 degrees . the gas is then allowed to expand in a cylinder containing an additional piston , and as a final cycle , additional fuel is added and ignited , and the resultant gases expand to drive an additional piston and provide further power to the engine . the pistons may all be coupled together to supply power to a single output drive shaft in the manner of an air motor . the exhaust gases are employed to warm the high pressure liquid air in a counter - current heat exchanger where exposure to moist ambient air would cause excessive ice buildup .