Ask a room full of BMW diesel owners which engine they'd trust with 400,000 km and you'll start an argument that lasts all night. One camp swears by the M57 — the straight-six that powered a generation of 330d and 530d saloons and refuses to die. The other points to the B57, the modern one, smoother and far more powerful, and asks why you'd live in the past.
Here's the thing the argument usually misses: they're both right. Both are BUY-grade in our database, and each has one big documented fault you can check for before you buy. This isn't a fight between a good engine and a bad one. It's a choice between two genuinely good ones.
Quick answer: The B57 (82/100) edges the M57 (78/100) on our scores, and both are BUY-grade. The M57's risk is the early metal swirl flaps (cars built to about 2004); the B57 has one recall to verify: the EGR cooler on 2017–2018 540d/40d cars. Buy the M57 for mechanical simplicity and cheap ownership; buy the B57 for refinement, power and modern manners.
The legend: M57 — 78/100 (BUY)
Built from 1998 to 2012, the M57 is the engine that made diesel respectable for enthusiasts. Cast-iron block, conventional turbocharging, and an appetite for mileage that became the stuff of forum folklore. The toughness is real — cars at around 400,000 km exist — but the record is not clean: the early metal swirl flaps (builds to about 2004) can break and fall into the cylinders, TÜ/TÜ2 exhaust manifolds crack, and injectors, turbo and the crank pulley damper wear with age. Blanking the flaps or replacing the intake manifold (about €580) removes the biggest risk.
What you're buying is honesty: an engine simple enough to maintain affordably, in cars old enough to be cheap, with a parts ecosystem that's been mature for a decade.
Found in: BMW 3 Series, 5 Series, 7 Series (525d, 530d), X5.
The successor: B57 — 82/100 (BUY)
The B57 arrived in 2016 as part of BMW's modular family, and it's a generational leap in everything — including, on our scores, dependability. Up to 400 hp in the hottest forms, vastly quieter, cleaner, and more efficient. Its one serious documented fault is the EGR cooler: on some 2017–2018 high-output cars (540d/40d) it can leak coolant into the intake, and BMW recalled them for a fire risk. Check the recall was done. Beyond that the data shows only the modern-diesel items — DPF loading on short trips and carbon in the intake and swirl flaps.
The trade is the modern one: more electronics, AdBlue/SCR emissions hardware, and tighter tolerances — a more complex car to own a decade from now.
Found in: BMW 530d, X5 30d.
And the one in between
Don't forget the N57 (69/100, ACCEPTABLE) — the 2008–2020 generation that bridges the two. It scores below both: most N57s are in the EGR-cooler fire recall (KBA 008124), and bearing wear is reported on engines with long oil-change intervals. Far more common on the used market than the B57, but buy one only with the recall done and a short-interval oil history — see N57 vs M57.
Old vs new, by the numbers
| M57 | B57 | |
|---|---|---|
| Years | 1998–2012 | 2016→ |
| Power | ~286 hp | up to 400 hp |
| Block | Cast iron | Aluminium, modular |
| Score | 78/100 | 82/100 |
| Biggest documented fault | Early metal swirl flaps (to ~2004) | EGR-cooler recall (2017–18) |
The verdict
The B57 takes it on points — but read that the right way. This is a four-point gap between two BUY-grade engines, each with one big fault you can check for: the swirl flaps on early M57s, the EGR-cooler recall on 2017–2018 B57s.
So choose by what you want from ownership:
- Want the cheapest path to a tough BMW diesel? The M57, in a tidy E-class-era 530d or X5, is one of the great used-car bargains — ideally a post-2004 car, or one with the swirl flaps already blanked.
- Want modern refinement and have the budget? The B57 gives you 100+ extra horsepower and a far nicer car, with a strong record — just confirm the EGR-cooler recall on 2017–2018 cars.
Curious how BMW's petrol six compares? See the B58 vs B57 showdown — petrol icon against diesel workhorse.
Scores are calculated from documented issues, repair costs, and failure patterns. Reviewed by the EngineScope editorial team. Methodology →