Best Maintenance Parts & Tools for the E30 (M20 / M42)
Keeping an E30 healthy is mostly about fitting quality parts from the right brands — these engines are simple, but cheap no-name components are a false economy. Here's the go-to parts list for the M20 six and M42 four, by job.
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M20 vs M42 — one key difference
Most service parts are shared, but the timing setup isn't. The M20 six uses a timing belt that's a scheduled replacement item. The M42 four uses a timing chain — no belt to replace, but it's prone to the lower-cover "profile gasket" failure. Buy timing parts accordingly (see the timing section below).
The Parts, by Job
FAQ
What's different between maintaining an M20 and an M42?
Day-to-day service is nearly identical. The big difference is timing: the M20 uses a timing belt that must be replaced on schedule, while the M42 uses a chain — no belt, but keep an eye on the profile gasket and chain tensioner.
Which brands should I trust?
OE manufacturers and OE suppliers: Mahle, Behr, Mann, Bosch, Beru, Lemförder, Bilstein, ATE and Zimmermann. Avoid the cheapest no-name parts — on cooling and ignition especially, they fail early.
How often does the M20 timing belt need doing?
Replace it on BMW's interval or by age if that's unknown — and always as a kit with the tensioner. The M20 is generally non-interference, but a failure still strands you, so don't gamble.
Do I need special tools?
Mostly no — basic hand tools, a torque wrench and a drain pan cover it. The one E30-specific item worth buying is a fan-clutch tool for cooling work.
Where should I start?
Oil and filters first, then the full cooling refresh — the most important job on these cars. Our tune-up and cooling guides walk both through step by step.
The Bottom Line
Stock up on quality, OE-grade parts and the E30 rewards you with classic reliability. Prioritize the cooling system and routine service, buy timing parts to match your engine — belt kit for the M20, chain components for the M42 — and lean on trusted brands throughout. Then put it to work with the tune-up and cooling guides. Back to the E30 hub for everything else.