Mercedes-Benz M264 (1.5 and 2.0)

Mercedes-Benz's 2.0 four-cylinder petrol engine — in 1.5 and 2.0 litre forms — and the first of the company's engines designed around a 48-volt belt-driven starter-generator as standard. Its successor is the M254.

That integration is the diagnostic frame. EQ Boost supplies torque fill, runs the stop-start and drives the ancillaries, so a complaint about rough starting, a hesitant pull-away or a charging warning is a question about the 48-volt system before it is a question about the engine.

The engine itself is a conventional modern direct-injection turbo four with the usual intake-valve carbon at mileage. Its long-term failure pattern is not yet established, which is worth stating rather than filling in by analogy — most of the material online concerns the hybrid system rather than the engine.

⚑ The 1.5 and the 2.0 are the same engine at two sizes, both with the integrated starter-generator, across five models here. The mild-hybrid system is what most complaints concern and it is common to both.