Petrol Fuel Engine

The burning fuel-air mixture in a cylinder produces gas temperatures of about 2500 °C. Therefore, the metal parts of the engine must be cooled or they would melt. Most automotive petrol engines are liquid cooled. A liquid, usually water, is circulated around the cylinders to cool the metal. The heated liquid is then pumped through a radiator. A fan driven by the engine or by an electric motor draws air through the radiator to cool the liquid.

Most aircraft reciprocating engines are air cooled to reduce weight. Air is not as effective a coolant as liquids, so the outsides of the cylinders have many metal fins. These fins conduct heat out of the cylinder and offer a large surface area for the air to sweep over, thus ensuring effective cooling.