Mercedes-Benz M260 / M270

The transverse four-cylinder petrol of Mercedes-Benz's front-drive platform — the A-Class, B-Class, CLA and GLA — in 1.6 and 2.0 litre turbocharged forms. The longitudinal M274 is its close relative, and telling the two apart is the first step in any parts or procedure lookup, because the family designation is nearly the only thing that separates them in a catalogue.

The engine also went to Infiniti for the Q30 and QX30, which shared the platform — so an Infiniti with a Mercedes engine is a real and often surprising diagnostic situation.

Camshaft adjusters, the timing chain and direct-injection carbon are the familiar themes. The one worth flagging is the turbocharger's oil feed on cars that have seen extended service intervals: this is a small, hard-working engine in a tightly packaged bay, and heat plus tired oil is the usual story behind a failed turbocharger rather than any defect in the turbocharger itself.

The M260 is the same engine's later revision — the A 250, A 35, CLA and GLB of 2015 onward — and carries the family's faults rather than a new set. The number says which revision, not which engine.