The inline-six behind the W124-generation E-Class — widely regarded as among the most over-engineered, durable engines Mercedes has ever produced, from an era when the company's reputation for building cars that simply didn't break was genuinely earned.
This engine's reputation isn't exaggeration — it was engineered during an era when Mercedes prioritised over-building its products well beyond what contemporary rivals attempted, and the real-world evidence (engines routinely exceeding 300,000 miles with only basic maintenance, many still in service decades later) backs that reputation up. There is remarkably little of chronic substance to warn a buyer about; at this point in the car's life, general age-related wear on surrounding systems matters far more than anything specific to this engine.
Not a guarantee, but a pattern seen consistently across owner forums and independent-garage reporting.
Timing chain and guide wear becomes a realistic, though still uncommon, consideration at very high mileage.
Numerous well-documented examples continue reliably at this stage and well beyond with only routine maintenance.
Beyond general age-related wear on surrounding systems, there's genuinely little engine-specific risk to flag on this legendary unit.
Inspect rubber seals, wiring and cooling hoses for age-related deterioration, now a bigger factor than the engine's own internals.
Find a specialist experienced with this era of Mercedes for sourcing increasingly rare surrounding-system parts.
Model-specific pages, with notes on how it behaves in that particular car.