What type of engine cooling does not use liquid coolant?

Air-cooled engines use air instead of liquid coolant to carry heat away.

In an air-cooled engine, heat moves from the cylinders and cylinder heads into the surrounding air. Designers commonly add cooling fins to increase surface area, and some engines use a fan or shrouding to direct airflow over those fins. The system avoids a radiator, water pump, coolant passages, and antifreeze.

Air cooling has been used in motorcycles, small utility engines, aircraft engines, and historic cars. The Volkswagen Beetle is one of the best-known mass-produced examples. Porsche also used air-cooled flat-six engines in many 911 models before switching to water cooling for the 996 generation in 1998.

Air cooling is not the same as oil cooling. Oil can help carry heat away in many engines, including air-cooled designs, but the defining heat-transfer medium is air. “Water-cooled” is also a common shorthand for liquid cooling, while hybrid systems may combine several methods rather than fit this single category.