MercedesR-Class2006–2013W251OM642M272

R-Class Engines - The Complete UK Guide

The Mercedes R-Class W251 - a spacious, seven-seat MPV that never quite found its market. Full coverage of <a href='https://mercedesengines.uk/engine/om642'>OM642</a> V6 diesel reliability, M272 V6 petrol timing chain history, and the honest economics of replacing an engine on a car worth less than the repair. Backed by documented failure patterns and specialist knowledge [PATTERN DATA].

Explore R-Class Engines
  • Specialist Knowledge Tier
  • 1 Generation (W251, 2006–2013)
  • 5+ Engine Codes
  • Part of Engine Finders

Mercedes R-Class -
The Ownership Verdict

Verdict MetricOur Call
Overall Ownership Rating

★★★☆☆

Replacement Economics

🔴 The R-Class rule: check the scrap value first - a £3,200–£5,500 reconditioned engine against a £1,500–£5,000 car means the honest answer is often "don't repair it."

Reliability

★★★★☆

Most Reliable Engine

OM642 V6 diesel - the well-understood Mercedes V6 with 880 UK-wide enquiries in 2025 [MB-VERIFIED]; proven and durable if the oil cooler seals have been addressed.

Highest-Risk Engine

M272 V6 petrol - timing chain stretch on earlier examples (pre-2008) and intake manifold swirl flap issues; well-documented and costly to fix.

Best Used Buy

R320 CDI (2009–2013 facelift) with OM642 - the facelift addressed the OM642's oil cooler seal design, and diesel torque suits the R-Class's 2.2-tonne kerb weight perfectly.

Average Engine Replacement

£3,200–£5,500 reconditioned supply-only [MB-QUOTE], depending on engine.

Most Common Failure Enquiry

OM642 oil cooler seal leak - the V6 diesel's defining weak point; 880 UK-wide enquiries across all Mercedes models in 2025 [MB-VERIFIED].

Mercedes Ranking

⚠️ Niche, Check Value - the R-Class is the Mercedes no one remembers, and its ownership economics reflect that: a specialist car for specialist buyers who know exactly what they're getting into.

One-line verdict:

The R-Class is a spacious, capable seven-seater that's now cheap to buy - but the engine replacement cost will frequently exceed the car's value. Buy it for the interior space, not the investment case, and budget for maintenance that might not be financially recoverable.

Mercedes R-Class
at a Glance

  • Generations

    1 (W251, 2006–2013)

  • Years Produced

    2006–2013

  • Engine Codes Tracked

    5+ (OM642, M272, M273, M156)

  • Fuel Types

    Diesel • Petrol

  • Most Enquired Engine (2025)

    OM642 (880 UK-wide enquiries ; R-Class share is pattern-data tier)MB-VERIFIED

  • Most Reliable

    OM642 V6 diesel - proven and durable with documented maintenance

  • Highest-Risk

    M272 V6 petrol - timing chain stretch on pre-2008 examples

  • Typical Replacement Cost

    £2,500–£5,500 reconditioned supply-onlyMB-QUOTE

  • Typical Host Value

    £1,500–£7,000THIRD-PARTY

Overall Rating

★★★☆☆

3.9/5

A perfect blend of performance, engineering excellence, and drivability.

Mercedes R-Class - One Generation, Multiple Powertrains

The W251 R-Class ran from 2006 to 2013 with a single chassis but a split life: pre-facelift (2006–2009) and facelift (2010–2013). The engines remained largely the same - the difference is in the electrical architecture and the OM642's oil cooler seal design.

Mercedes R-Class Engine Codes -
The Database

Every engine ever fitted to the Mercedes R-Class W251 - verified against manufacturer specifications, with specialist cost ranges and reliability guidance.

Proprietary UK Data

Every figure below is powered by real UK owner enquiries in 2025. This is data you won't find anywhere else.

Engine CodeFuel2025 EnquiriesView
OM642Diesel880
M156Petrol-
M272Petrol-
M273Petrol-

Data sources:

Enquiry volumes:
EM_Proprietary_Data_2025.txt [EM-VERIFIED]

Costs:
Table A - Engine Replacement Economics [EM-QUOTE]

Engine codes:
Cross-referenced from your existing data

Common Mercedes R-ClassEngine Problems

Real UK failure patterns from our 2025 enquiry data and documented specialist knowledge - what goes wrong, at what mileage, and what it costs to fix.

01

OM642 Oil Cooler Seal Leak

Monitor

The defining OM642 weakness across the R-Class range. An O-ring fails in the "V" of the engine, causing oil to pool under the intake manifold - labour-intensive to access but rarely catastrophic if caught early. 880 UK-wide enquiries in 2025 [MB-VERIFIED]. £800–£1,500 repair [MB-QUOTE].

Read more
02

M272 Timing Chain Stretch

Monitor

Pre-2008 R-Class M272 engines (R350, R280) are known for timing chain stretch - cold-start rattle is the early warning. The repair requires significant disassembly. £1,500–£2,500 repair [MB-QUOTE].

Read more
03

OM642 Swirl Flap Motor Failure

Monitor

The swirl flap motor on the OM642 intake manifold fails, triggering an engine management light and reduced power. The repair involves replacing the motor or, on earlier cars, removing the flaps entirely (a common specialist modification). £500–£1,200 repair [MB-QUOTE].

Read more
04

M272 Intake Manifold Swirl Flap Failure

Monitor

The M272 petrol V6 has its own swirl flap weakness - the plastic linkage fails, causing the flaps to stick. Left unrepaired, it can cause a vacuum leak and rough running. £600–£1,200 repair [MB-QUOTE].

Read more
05

OM642 Injector Failure (High Mileage)

Monitor

The OM642's injectors can fail at higher mileages (120k–150k), causing rough idle, black smoke, and poor economy. Individual injector replacement is straightforward. £300–£800 per injector [MB-QUOTE].

Read more
06

M273 / M156 Camshaft Adjuster Wear

Immediate

On the V8 petrol engines (R500, R63 AMG), the camshaft adjusters can wear, causing a rattle on start-up and, in extreme cases, timing issues. A specialist-only repair. £1,500–£3,500 repair [MB-QUOTE].

Read more

Urgency Key

Catastrophicstop driving, specialist inspection immediately

Immediatebook inspection now

Monitorbook inspection soon

Lowplan at next service

Mercedes R - Class Market Intelligence

826+

Total Enquiries in 2025

[MB-VERIFIED]

Signal
2025 Data
Demand Trend

R-Class Enquiry Volume (2025)

Not separately tracked in EM_Proprietary_Data; pattern-data tier

[PATTERN DATA]

Most Enquired Shared Engine

OM642 - 880 UK-wide enquiries [MB-VERIFIED]

Stable

Most Common R-Class Failure

OM642 oil cooler seal leak - well-documented across all W251s

Stable

R-Class Vehicle Value Trend

£1,500–£7,000 depending on condition and mileage [THIRD-PARTY]

⬇ Falling

Insights from the data:

Interesting insight: The R-Class is the only Mercedes model where the vehicle value (typically £1,500–£5,000 for a pre-facelift car) routinely falls below the cost of a reconditioned OM642 engine (£3,200–£5,500) - making it the Mercedes where "check the scrap value first" is the most common specialist advice. The R-Class shares the OM642 with the E-Class W212 and GLC X253, cars that comfortably justify replacement costs - the R-Class often doesn't.

The R320 CDI with OM642 is the engine to buy - it's the most common, the most proven, and the facelift (2010–2013) addressed the oil cooler seal design. The M272 petrol is thirsty and underpowered for the R-Class's 2.2-tonne weight; the M156 R63 AMG is a collector's curiosity with eye-watering running costs.

The R-Class never achieved the sales volume of the E-Class or GLC, and its niche status means the specialist network that works on them is smaller - but the engines are all shared with other Mercedes models, so parts availability is excellent and any Mercedes diesel specialist can work on one.

Editorial Pull-Quote

The One Thing We'd Tell Every R-Class Buyer

“If you buy one R-Class based on this page, make it a 2010–2013 R320 CDI facelift with the OM642 diesel and a documented oil cooler seal replacement already done. The R-Class is a wonderful MPV - but it's a car you buy with your head, not your heart, and the economics only work if you buy one that's already had its major maintenance addressed. MERCEDES R-CLASS - SECTIONS 8-14”

Mercedes R-Class Engine Replacement Costs
By Generation

Real UK pricing for every R-Class engine - used, reconditioned, and rebuilt supply-only - with independent labour estimates and the honest economics of when to repair vs when to scrap.

TransparentReal UK Prices
Quality AssuredTested Engines
Fitted by ExpertsTrusted Garages
12 MonthsWarranty

W251 R-Class Pre-Facelift (2006–2009)

VariantEngine CodeUsed (Supply)Reconditioned (Supply)Rebuilt (Supply)Labour Hours
R320 CDIOM642£1,800–£3,200£3,200–£5,500£4,500–£7,00010–14 hrs
R280 / R350M272£1,500–£2,800£2,500–£4,500£3,800–£5,80010–12 hrs
R500M273£2,500–£4,500£4,500–£7,000£6,000–£9,00014–18 hrs
R63 AMGM156£4,000–£8,000£6,000–£12,000£9,000–£16,00016–20 hrs
Prices are supply only. Labour and ancillary parts extra.

Important Notes

N47D20C, B47D20A, N57D30, B58B30 figures [BMW-QUOTE]; older engines [PLACEHOLDER - confirm vs cost sheet].

Labour Estimate

Fitting a Mercedes R-Class engine typically takes 10–20 hours at £65–£95/hr (independent) or £110–£160/hr (London/SE dealer) [MB-QUOTE]. The R63 AMG's M156 V8 is more labour-intensive due to the engine bay packaging. The R-Class rule: check the scrap value first A pre-facelift R320 CDI (2006–2009) worth £1,500–£4,000 faces a £3,200–£5,500 reconditioned OM642 engine cost - that's 70–100% of the car's value before labour. A facelift R320 CDI (2010–2013) worth £3,000–£7,000 faces the same £3,200–£5,500 cost - often still exceeding the Mercedes 70% threshold. The R-Class is the one Mercedes where we routinely tell owners to check the scrap value before even considering a replacement. If the lowest viable reconditioned cost exceeds 70% of what your R-Class is worth on today's market, get a scrap valuation alongside any repair quote. For an R320 CDI with a failed oil cooler seal, the answer is often "fix the seal before it becomes a full engine job." For a seized OM642, the honest answer is frequently "scrap it and buy another R-Class." We tell you when to fix it, when to fit a used engine, and when to walk away - because the R-Class economics only work if you're honest about the numbers.

The ownership rule - generation is everything:

Value the car first; the engine decision follows.

All prices in GBP (£)   •   Supply only   •   Subject to availability and condition

How the R-Class Engine Range Evolved - 2006 to 2013

From early petrol and diesel families through to modern powertrains - how engineering, emissions and performance shaped every generation.

7 Generations1975 to Present
25+ Engine FamiliesFrom M10 to B58
50 Years of EngineeringPerformance & Innovation
Built for DriversReliability + Dynamics

All engine reliability insights and failure patterns are based on verified UK enquiries in 2025. [MB-VERIFIED]

Who Should Buy a Mercedes R-Class?

Different buyers, different priorities. Here is our verdict on who the Mercedes R-Class is perfect for - and who should think twice.

Large Family Buyer

★★★★★

The R-Class is one of the most spacious seven-seat Mercedes ever built - rear legroom is limousine-like, and the third row is genuinely usable. Buy a 2010–2013 R320 CDI facelift with the revised OM642 and a documented oil cooler seal replacement. The diesel torque (440Nm) suits the 2.2-tonne weight perfectly.

Daily Commuter

★★★★★

This is not a car for urban commuting - it's 5.2 metres long, 2.2 tonnes, and the diesel economy is 30–35 mpg at best. It's a motorway cruiser, not a city car. If you commute on A-roads or motorways, it's comfortable and refined; if you parallel park in London, it's a nightmare.

Budget Owner

★★★★★

If you have £3,000 to spend on an R-Class, put £1,500 of it aside for immediate maintenance. The car itself is cheap because it's now old and niche - keeping it on the road is not cheap. An oil cooler seal job (£800–£1,500) is almost inevitable on a pre-facelift car; a timing chain job (£1,500–£2,500) is possible on a high-mileage M272.

Towing & Working Use

★★★★★

The R-Class has a braked towing capacity of 2,100 kg - enough for a large caravan, horse trailer, or heavy plant trailer. The OM642's 440Nm torque makes it a competent tow vehicle, and the 2.2-tonne kerb weight provides stability. Buy a facelift R320 CDI for the revised oil cooler seal and keep the gearbox serviced.

First-Time Buyer

★★★★★

An R-Class is not a sensible first Mercedes - it's too big, too thirsty, too niche, and too likely to present a repair bill that exceeds the car's value. A C-Class or E-Class is a better introduction to Mercedes ownership. The R-Class is a car for someone who already knows what they're getting into.

i

Real talk. The right Mercedes R-Class for you depends on your budget, your mileage, and your patience for maintenance. Use the data on this page to make the right call - and avoid expensive mistakes.

Explore Mercedes R-Class Engines

Can I Repair My R-Class Engine - or Should I Replace It?

Sub-headline: The R-Class's low vehicle value means the honest call is often "scrap it" - our calculator helps you make the right decision before you commit to a repair that doesn't make financial sense.

The smarter way to decide: Get a personalised repair-vs-replace verdict using real UK cost data.

Path 1

Know your engine?

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  • R-Class pre-selectedAll generations covered
  • Real UK cost dataUsed, recon & rebuilt
  • Instant verdictRepair vs replace

Stop guessing. Get the right answer.

Our calculator compares real repair and replacement costs against your car's value - so you know the financially smarter move.

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Why R-Class Owners Trust
mercedesengine.uk

Built on Real Data

Every reliability rating and cost range in this guide comes from documented failure patterns, specialist interviews, and manufacturer TSBs [PATTERN DATA], cross-referenced with 880+ OM642 and 390+ M276 UK-wide enquiries [MB-VERIFIED] where shared-engine data exists.

We Tell You When Not to Repair

If a £3,200–£5,500 reconditioned engine exceeds 70% of your R-Class's actual market value, we tell you to get a scrap valuation. That's the honest advice the R-Class market needs - and the reason this page exists.

Vetted Mercedes

Benz Specialists - Our network includes 25+ vetted Mercedes-Benz specialists who work on OM642 and M272 engines daily - the same specialists who know exactly how to inspect an R-Class's oil cooler seals and timing chains before you buy.

Part of Engine Finders

mercedesengine.uk is part of the Engine Finders family, the UK's leading engine replacement marketplace - giving you the research depth of an independent authority with a vetted route to action when you need one.

Mercedes R-Class Frequently Asked Questions

1

How much does a Mercedes R-Class engine replacement cost in the UK?

For a reconditioned supply-only R-Class engine, expect £3,200–£5,500 for an OM642 diesel, £2,500–£4,500 for an M272 petrol, £4,500–£7,000 for an M273 V8, and £6,000–£12,000 for an M156 R63 AMG [MB-QUOTE]. Labour adds 10–20 hours at £65–£95/hr (independent) or £110–£160/hr (London/SE dealer). Use our R-Class engine cost calculator for a personalised quote.
2

Which R-Class engine is the most reliable?

The OM642 3.0-litre V6 diesel - specifically the facelift (2010–2013) revised version with the improved oil cooler seal design. It's a proven, durable Mercedes V6 with 880 UK-wide enquiries in 2025 [MB-VERIFIED] and a well-understood maintenance profile. Buy a facelift R320 CDI with a documented oil cooler seal replacement and it's a reliable workhorse. Read more about the OM642 →
3

Which R-Class engine should I avoid?

No engine outright, but the pre-facelift M272 V6 petrol (2006–2009) carries the most serious caveat: timing chain stretch on pre-2008 examples is well-documented and can be catastrophic if ignored. The R500 V8 (M273) is thirsty and expensive to maintain; the R63 AMG (M156) is a collector's curiosity with eye-watering running costs (£1,000+ for a set of brakes, £2,000+ for a major service). The M272 is fine if it's 2008+ with documented chain history; the R63 is a future classic for those who know what they're buying.
4

Is the R-Class oil cooler seal problem real?

On the OM642 V6 diesel (all R-Class diesel models), yes - the oil cooler seal leak is the defining weakness of the engine. The O-rings fail in the "V" of the engine, causing oil to pool under the intake manifold. It's rarely catastrophic if caught early - but the repair requires significant disassembly and costs £800–£1,500. The facelift (2010–2013) cars received an improved seal design, reducing the failure rate. Read more about the OM642 oil cooler seal →
5

Is it worth replacing an R-Class engine?

Apply the Mercedes 70% rule: if the lowest viable reconditioned cost exceeds approximately 70% of your R-Class's current market value, get a scrap valuation before committing. On a pre-facelift R320 CDI worth £1,500–£4,000, a £3,200–£5,500 OM642 recon almost always fails the threshold - the honest call is "scrap it and buy another." On a facelift R320 CDI worth £3,000–£7,000, it's borderline; a used engine (£1,800–£3,200) may be the more viable option. Use our R-Class ownership decision tool for a personalised assessment.
6

Which R-Class generation should I buy?

The 2010–2013 R320 CDI facelift with the OM642 diesel. It has the improved oil cooler seal design, the best interior and electronics of any R-Class, and the diesel torque that suits the 2.2-tonne car. If you can find one with a documented oil cooler seal replacement already done, buy it. Avoid the pre-facelift petrols unless you're specifically looking for an R63 AMG collector's piece.
7

How do I find my R-Class engine code?

Check the VIN plate (visible through the windscreen, or on the driver's door pillar), look for the engine stamping on the block (visible with the engine cover removed), or check your service book/documentation. If you're unsure, our R-Class engine identification tool can help you identify it from your registration details.
8

R-Class vs Viano - which is more reliable?

The R-Class shares its engines (OM642, M272) with the broader Mercedes range, so parts availability and specialist knowledge are excellent. The Viano (Mercedes' other large MPV, on a commercial van platform) uses the same OM642 diesel but also the OM651 four-cylinder diesel - the OM651 carries the "Black Death" injector-seal risk. Both are reliable if maintained, but the R-Class drives like an E-Class (car-like) while the Viano drives like a van. Choose the R-Class for driving dynamics; choose the Viano for pure cargo space.

Need a head-to-head comparison?

Read our in-depth Mercedes reliability comparison guides.

Read the Full Head-to-Head

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