Mercedes-Benz GLC X254 — Reliability

X254 2026–present 1 engine

Reliability Summary

Engine M256 — 88/100 BEST
Known Issues 3

Engine in this model

BEST 88

M256

3.0L Turbo 48V I6

Mercedes returned to a straight six in 2017: 3.0 turbo with a 48V starter-generator (EQ Boost), in t...

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Known Issues Across All Engines

Issue Engine Severity Onset
48V system faults — starter-generator, wiring and battery software (recalls) M256 moderate 64,000 km – 129,000 km
Timing chain tensioner wear — unconfirmed M256 minor 129,000 km – 193,000 km
Oil leaks — valve cover / front cover gaskets M256 minor 97,000 km – 129,000 km