The Volkswagen air-cooled engine is an air-cooled, gasoline-fuelled, boxer engine with four horizontally opposed cast-iron cylinders, cast aluminum alloy cylinder heads and pistons, magnesium-alloy crankcase, and forged steel crankshaft and connecting rods. There are two distinct families/variations of the aircooled engine namely Type 1 and Type 4. The Type 3 engine is a variation of the Type 1 engine with pancake cooling arrangement.