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Mercedes OM651
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Mercedes OM651
Verdict
RISKY · 48/100
Est. cost /3yr
€1,500–4,500 over 3 years depending on mileage and chain condition at purchase
Oil interval
10,000 km
Recalls
1
Worst issue
Timing Chain Stretch & Tensioner Failure
CRITICAL
Mercedes OM651
X253 · X253
Timing Chain Stretch & Tensioner Failure
€1,200-3,500
CRITICAL
Oil Leaks — Rocker Cover & Oil Filter Housing
€300-900
HIGH
Oil Pressure Smart Valve / Blanking Plug Leaks
€200-600
HIGH
Thermostat & Coolant System Failure
€250-700
MODERATE
Intermittent Starting Issues
€400-1,500
MODERATE
Transmission Mount Wear
€150-400
LOW
Mercedes OM651
X253 · X253
•Cold-start the engine and listen for timing chain rattle in the first 10-30 seconds, walk away if present
•Check full oil service history; verify intervals did not exceed 10,000 km or 12 months
•Inspect rocker cover top and oil filter housing base for fresh oil leaks or heavy residue
•Confirm engine reaches normal operating temperature within 10-15 minutes of driving, suspect thermostat if it does not
•Scan for fault codes including timing, fuel pressure, glow plug and coolant temperature faults before purchase
•Check transmission and engine mounts for deterioration, especially on 4MATIC variants with higher mileage
•Confirm whether the NOx emissions software recall has been completed via dealer service records
Mercedes OM651
X253 · X253
Timing chain & tensioner
Inspect at purchase; replace chain, tensioner and guides as a kit if rattle present or over 120,000 km
120,000 km
Oil filter housing gasket / base seal
Inspect for leaks at every service; replace seal proactively during any oil system work
100,000 km
Thermostat
Test engine warm-up rate; replace if engine struggles to reach operating temperature
100,000 km
Rocker cover gasket
Inspect for oil seepage at top of engine; replace gasket if weeping
120,000 km
Mercedes OM651
X253 · X253
Engine Control Unit Software (NOx Emissions)
Following KBA (German motor authority) investigations into diesel emissions compliance, Mercedes-Benz issued a mandatory ECU software recall covering a large range of Euro 5 and Euro 6 OM651 powered vehicles, including GLC 220d, for NOx emissions exceeding limits in real-world driving conditions.
Mercedes OM651
X253 · X253
✓Proven engine architecture used across a wide Mercedes model range
✓Known failure modes are well-documented and predictable
✓Good power and torque output for a 2.1-litre diesel
✓Strong long-term durability when oil changes are kept to short intervals
✓Extensive parts availability and independent specialist knowledge
Mercedes OM651
X253 · X253
Real consumption
7 L/100km
Official consumption
Not available
Oil interval
10,000 km
Oil spec
MB 229.51 or MB 229.52 5W-30 fully synthetic
Est. cost /3yr
€1,500–4,500 over 3 years depending on mileage and chain condition at purchase