M20

1977–1993•6 cyl•Inline•Al / cast_iron

Successor: M50 →

Timing belt (requires replacement every 80–100k km)
Cast iron block with aluminium head
Wide range of displacements and power levels

The BMW M20 is a legendary inline-6 petrol engine produced from 1977 to 1993. It powered E21, E30, E28, E34. Cast iron block, aluminium head, SOHC, timing belt. Smooth, reliable, and easy to maintain. Displacements from 2.0 to 2.7 litres, with famous 325i (2.5 L, 170 hp) and 325e (2.7 L low-end torque). Predecessor to the M50.

Known issues: timing belt replacement every 80–100k km, and overheating risk with aging cooling system. Capable of over 400,000 km with proper care.