BMW Engine Reliability Guides
Engine-specific buyer intelligence for UK used BMWs. Common faults, mileage danger zones, real UK repair costs, preventative schedules, and a straight buy/negotiate/walk verdict on each engine family.
Why engine code matters
A "520d" can be an N47, B47, N57 or B57 depending on year. These engines have very different reliability profiles and very different UK repair-cost exposures. Matching the right guide to your listing is the difference between a confident buy and an expensive surprise.
Pick your engine
Not sure which engine is fitted?
Start with the BMW chassis × engine codes reference — look up any BMW by year, model, or badge to find the exact engine family. Then come back here for the buyer guide.
Coming soon
Editorial expansion of the engine database, in priority order:
- B58 — 3.0L straight-six petrol (M140i, M240i, 340i, 440i, 540i, Z4 M40i)
- B48 — 2.0L four-cylinder petrol (318i, 320i, 330i, X3 20i)
- N20 — 2.0L four-cylinder petrol predecessor to B48 (timing-chain warning on this one)
- S55 — M3/M4 F80/F82 (crank-hub concern)
- S58 — current M3/M4/X3M/X4M
- N63 / N63TU — V8 petrol (oil-consumption warning)
Check a specific BMW listing
Paste any BMW listing, VIN, or reg plate — Bimmer.AI picks the right engine, pulls the right failure patterns, and returns a 30-second buyer report.
Run a Bimmer.AI buyer report →