The 2022 GLE350d W167 with OM656 diesel is generally solid but shares the catastrophic oil dilution issue plaguing OM656 engines worldwide. When it hits, you're looking at complete engine failure requiring rebuild or replacement—this is the defining risk of ownership.
OM656 Diesel Fuel Dilution / Catastrophic Engine Failure
Occasional · high severityTypical onset: 30,000-80,000 mi
Symptoms: Rapidly rising oil level on dipstick between changes, Thin, fuel-smelling oil, Rough idle, misfires, loss of power, Sudden rod knock or complete seizure if undetected
Fix: Fuel leaks past injector seals or faulty regeneration cycles dilute oil, washing bearings and scoring cylinder walls. Fix requires full engine teardown: pistons, rings, bearings, often crankshaft polish or replacement. 40-60 hours labor for short block or full rebuild. Some cases covered under extended MB warranty campaigns—check TSBs.
Estimated cost: $15,000-28,000
9G-Tronic Transmission Oil Cooler Leaks
Common · medium severityTypical onset: 50,000-90,000 mi
Symptoms: Transmission fluid seeping around cooler lines or housing, Low fluid warnings on dash, Harsh shifting or slipping when fluid drops significantly
Fix: Cooler seals deteriorate, especially in hot climates or heavy towing. Replace cooler assembly and flush system, refill with MB-spec ATF. 4-6 hours labor depending on access.
Estimated cost: $1,200-2,200
Transmission Mount Deterioration
Common · low severityTypical onset: 60,000-100,000 mi
Symptoms: Clunk or thud on acceleration or deceleration, Vibration at idle in Drive, Visible rubber cracking or separation on mount
Fix: The W167 9-speed transmission mount wears faster than expected, especially with diesel torque. Straightforward R&R, 2-3 hours with proper lift access.
Estimated cost: $600-1,000
Diesel Particulate Filter (DPF) Clogging and Regen Issues
Occasional · medium severitySymptoms: Check engine light with P2002 or P242F codes, Limp mode or reduced power, Excessive forced regens, Poor fuel economy
Fix: Short-trip driving or failed sensors prevent proper DPF regeneration. Often requires forced dealer-level regen first (1 hour), but if filter is ash-loaded or cracked, replacement is $2,500-4,000 in parts alone plus 3-5 hours labor. Preventive: monthly highway runs at steady speed.
Estimated cost: $3,000-5,500
AdBlue (DEF) System Faults
Occasional · medium severityTypical onset: 40,000-80,000 mi
Symptoms: AdBlue warning: 'Refill, XXX miles to no start', Check engine light with NOx sensor codes, Heater or pump failure messages in winter
Fix: Heater elements, level sensors, or NOx sensors fail. Pump replacement is 3-4 hours, NOx sensors 2-3 hours each. Crystallized DEF from cheap fluid accelerates failures—use only quality AdBlue and keep tank above 1/4.
Estimated cost: $800-2,500
Airmatic Suspension Compressor and Strut Leaks
Occasional · medium severityTypical onset: 70,000-120,000 mi
Symptoms: Vehicle sagging overnight (one corner or全车), Compressor runs constantly, Suspension warning on dash, Rough ride or bottoming out
Fix: Air struts develop leaks at bellows or seals; compressor wears from overwork. Front strut 3-4 hours each, rear 2-3 hours. Compressor 4-5 hours. Address leaks immediately to save compressor.
Estimated cost: $1,500-3,500
The OM656 fuel dilution grenade makes this a hard pass unless you have documented proof of engine health and a strong warranty—too much downside risk for the price.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.