Why it's a good car
The 2015 ML350 is the final model year of the ML name — it became the GLE for 2016 — built on the W166 platform. It runs the M276 3.5-liter V6 (about 302 hp), the improved replacement for the trouble-prone M272, paired with the 7G-Tronic Plus seven-speed automatic and full-time 4MATIC all-wheel drive. Looked after, these regularly pass 200,000 miles. The engine is durable; the conditions below are about the systems around it.
Does it have a timing belt or a timing chain?
A timing chain. The M276 V6 is chain-driven, so there is no belt to replace. Listen for a brief cold-start rattle from the camshaft-adjuster area; a clean, quiet cold start is what you want.
The things to check before you buy
- Suspension type AIRMATIC air suspension was optional on the W166 — many left the factory on conventional steel coils. Find out which this car has, because the air suspension is the single biggest financial risk on these: it should sit level after sitting overnight, rise evenly on all four corners and hold, with the compressor not straining. A steel-sprung car dodges that bill entirely.
- Transmission fluid The 722.9 is not truly "sealed for life" — you want a service record and clean shifts cold and warm, with no flare or hunt.
- Fuel-pump recall There is an open recall on these (2012–2020 ML/GLE) for water getting into the spare-wheel-well fuel-pump control unit, which can cause a sudden loss of propulsion. Lift the cargo-floor cover, check the spare-wheel well for water or staining, and confirm the recall was performed — the fix is free at a Mercedes dealer.
- Cold-start rattle and coolant tank The M276 cold-start camshaft-adjuster rattle and a cracking plastic coolant expansion tank are ordinary items to check at this age.
- Proper diagnostics These need a Mercedes-capable scan tool to read the transmission, air-suspension, and SRS modules, not just a generic reader.
What would make you walk
- A tired air suspension Any corner sagging overnight, a system that will not rise and hold level, or a lit suspension fault, with no recent work.
- A wet spare well and an open recall Water or rust in the spare-wheel well with the fuel-pump recall not completed.
- A tired transmission Harsh or flaring shifts, or hunting between gears.
- Coolant in the oil Cream or mayonnaise residue under the oil cap.