Lightness over torque
The M42 does its best work higher in the rev range. In a two-door 318is it keeps weight over the front axle down and gives the chassis an eager balance. Calling it a ‘baby M3’ is convenient shorthand, but the road car has its own identity and should be judged on condition rather than the nickname.
Chain guides and oil leaks
Listen for persistent chain rattle, especially at start-up, and inspect the timing-case area for leaks. Later replacement parts and previous repairs matter. Vacuum leaks and aged intake hoses can cause unstable idle, while cooling-system neglect remains a threat despite the chain-driven camshafts.
Buying an M42 E30
A genuine 318is combines the engine with model-specific suspension and equipment, so verify identity and originality. Modified cars can be excellent, but assess the quality of every change. A standard airbox, intact wiring and documented maintenance often say more than polished wheels and a loud exhaust.