BMW M57 (2.5–3.0)

The straight-six diesel that established BMW's reputation for large fast diesels — common-rail, turbocharged, in 2.5 and 3.0 litre forms, and fitted to almost everything from the 3 Series to the X5 across fifteen years.

Unlike the four-cylinder N47 that ran alongside it, the M57's timing chain is at the front of the engine, which is the single most useful thing to know about it: the N47's expensive rear-chain failure does not transfer, and treating the two as the same problem misprices the repair badly in both directions.

What it does suffer is intake-side carbon and swirl-flap failure — the flaps' spindles wear and, on some versions, a flap can be drawn into a cylinder, which ends the engine. Many have had the flaps removed or blanked, so establishing what is actually in the intake matters before diagnosing an airflow complaint. EGR cooler blockage and, at high mileage, injector and turbocharger wear complete the picture.

One designation across three displacements, and the cars listed below carry two of them. The first M57D30 was 2.9 litres — the early 530d, 730d and the Range Rover Td6 — and was enlarged to 3.0 for the second generation, with a 2.5 beneath both. The chain-at-the-front fact above holds for all of them. A part number does not.