The most common types of engines used in automobiles are diesel and gasoline engines. Both types of engines run on liquid fuel. Gasoline and diesel oil are all produced from natural petroleum and are distinguished mainly by their volatility, that is, the ease with which they can be changed from a liquid to a vapor.
Both types of engines are internal-combustion engines, that is, they burn the fuel inside their cylinders. Most engines work on the four-stroke cycle: the piston makes a suction stroke (down), a compression stroke (up), a power stroke (down), and an Automobile Engines exhaust stroke (up). But a diesel engine has no ignition system. In it fuel is ignited simply by contact with very hot air which was highly compressed in the cylinder. A diesel engine draws into its cylinder air alone, and it compresses this air on its compression stroke before any fuel enters the cylinder. A gasoline engine mixes air with fuel before it enters the engine through the inlet valve during the suction stroke. Diesel engines use greater compression than gasoline engines. Diesel engines use less volatile, heavier liquid fuels than gasoline engines. These heavier fuels are generally Automobile Engines cheaper than gasoline. Fuel pumps and injection nozzles are used in diesel engines to inject the oil into the cylinder in the form of a fine spray. Diesel engines are heavier than gasoline engines of the same size because they work against greater pressures, and consequently their parts must be stronger.