Mercedes Benz M Class 250 BlueTEC/350 BlueTEC Engine Replacement Compare Prices & Get Quotes

Short summary: A rebuilt OM651 engine for the ML 250 BlueTEC costs £2,500-£3,500 supply-only; a rebuilt OM642 engine for the ML 350 BlueTEC costs £3,500-£4,800 supply-only. Fitting adds £800-£1,500 depending on complexity - BlueTEC emissions systems require specialist knowledge.

• ML 250 BlueTEC (OM651.960): rebuilt unit £2,500-£3,500; used engine from £1,200
• ML 350 BlueTEC (OM642.826): rebuilt unit £3,500-£4,800; used engine from £1,800
• OM651 timing chain tensioner replacement: £400-£700 at specialist
• OM642 oil cooler seal replacement: £900-£1,400 at specialist

Short summary: Oil leaks from around the chain tensioner gasket area are the classic warning sign on the OM651 engine. Mercedes issued a recall for 2015 ML 250 BlueTEC models over this issue. Leaking oil may drip onto a hot engine surface, increasing fire risk.

• Oil leak from chain tensioner gasket area
• Oil dripping onto hot engine surfaces - fire risk
• Check your VIN for outstanding recall status
• If recall doesn't apply, specialist repair costs £400-£700

Short summary: The OM642 V6 is a fundamentally strong engine, but BlueTEC variants face emissions system challenges. DPF, AdBlue, and EGR system issues are common, with owners reporting persistent check engine lights. Oil cooler seal degradation is also a known weakness.

• OM642 V6 is fundamentally robust with good longevity
• AdBlue/SCR system faults are the most common issue
• Oil cooler seal degradation affects many units
• Well-maintained OM642 BlueTEC engines exceed 150,000 miles

Short summary: Properly maintained OM651 and OM642 BlueTEC engines routinely reach 150,000-200,000 miles before major work. However, BlueTEC emissions components (AdBlue, DPF, EGR) may require attention from 60,000 miles.

• OM651 (250 BlueTEC): 150,000-200,000+ miles with regular servicing
• OM642 (350 BlueTEC): 150,000-200,000+ miles with proper maintenance
• Timing chain tensioner gasket issues may appear from 40,000 miles
• AdBlue/SCR system faults can occur from 60,000 miles

Short summary: Yes, if the M Class is otherwise in good condition with no rust or major transmission faults. A rebuilt OM651 costs £2,500-£3,500 - far less than replacing an £8,000-£20,000 vehicle. The ML 350 BlueTEC's higher value (£10,000-£20,000) makes replacement even more financially justifiable.

• ML 250 BlueTEC values: £8,000-£16,000 depending on year, mileage and condition
• ML 350 BlueTEC values: £10,000-£20,000 - premium SUV residual values remain strong
• Rebuilt engine with upgraded components fixes original weak points
• Supply & fit typically £3,300-£6,300 depending on engine code
• New engine includes 12-month unlimited mileage warranty

Short summary: Mercedes-Benz specifies low-SAPS oil meeting MB 229.51 or 229.52 - typically 5W-30. The OM651 requires approximately 6.5 litres; the OM642 V6 requires approximately 8.5 litres.

• OM651 (250 BlueTEC): MB 229.51/229.52 5W-30 low-SAPS - protects DPF and AdBlue systems
• OM642 (350 BlueTEC): MB 229.51/229.52 5W-30 low-SAPS - 8.5L capacity
• Never use non-approved oil - can cause DPF and AdBlue system damage
• Change every 10,000 miles or 12 months - stretched intervals cause timing chain and emissions issues