S Class Diesel Engines
from £2,800 to £5,500
Rebuilt units from £2,800 · Common codes: OM656, OM642, M276
Mercedes Benz ENGINE MARKETPLACE
Mercedes S Class M256/M176/M177 Specialist Engine Replacement - Compare Quotes
Get specialist quotes from UK Mercedes S Class engine experts. Compare reconditioned & rebuilt engines for S 350 to S 65 AMG - M256/M176/M177 covered. Get specialist quotes for your S Class.
Supply & Fit Available
12-Month Warranty
Nationwide Delivery
100+ Suppliers
S Class Petrol Engines
from £3,500 to £7,200
Rebuilt units from £3,500 · Common codes: M278, M256, M276
S Class AMG Engines
from £6,500 to £12,000
Rebuilt units from £6,500 · Common codes: M177, M279, M176
Instant engine replacement quote - 100% free, no obligation
Engine replacement near me - UK-wide specialist network
Compare reconditioned, rebuilt & used engine prices
Supply & fit available - parts and labour from vetted specialistsInstant engine replacement quote - 100% free, no obligationEngine replacement near me - UK-wide specialist networkCompare reconditioned, rebuilt & used engine pricesSupply & fit available - parts and labour from vetted specialistsHow It Works
3 Simple Steps3 Simple Stepsto Finding the Best Mercedes Benz S Class Replacement Engineto Finding the Best Mercedes Benz S Class Replacement Engine
12-Month Warranty
Supply & Fit Available
Nationwide Delivery
Trusted UK Suppliers
Most replacements completed within 3-5 days.
Live UK Engine Market Data
What Are UK Drivers Paying for Mercedes Benz S Class Engine Replacement
This table details typical UK rebuilt engine replacement costs across Mercedes Benz S Class variants, covering failure causes, engine codes, fuel types and displacements.
Average Market Prices
↻ Last updated: 4 Aug 26, 9:26
Customer Reviews
Trusted by Mercedes Benz S Class Owners Across the UK
Rated 4.8 out of 5 by 1,081 verified customers who sourced reconditioned and used Mercedes Benz S Class engines through EngineMarket.
4.8
★★★★★
out of 5
1,081 verified reviews
★★★★★
“Thanks to EngineMarket, I saved over £1,200 on my engine replacement and got matched with a great local specialist within the hour.”
JJimmyGoogle
★★★★★
“Got three quotes within an hour and chose the best deal easily. The whole process was quick, clear and stress-free.”
PPeteFacebook
★★★★★
“I wasn't sure what I needed, but they helped me identify the right engine and connected me with a trusted garage.”
SSophieTrustpilot
★★★★★
“Thanks to EngineMarket, I saved over £1,200 on my engine replacement and got matched with a great local specialist within the hour.”
JJimmyGoogle
Variants We Cover
Mercedes Benz S Class Engine ReplacementAll Variants Covered
Mercedes Benz S Class S350d
OM656 3.0L Diesel
Rebuilt Engines: £2,400-£3,900
Mercedes Benz S Class S400d
OM656 3.0L Diesel
Rebuilt Engines: £2,600-£4,300
Mercedes Benz S Class S350d 4MATIC
OM656 3.0L Diesel
Rebuilt Engines: £2,500-£4,100
Mercedes Benz S Class S400d 4MATIC
OM656 3.0L Diesel
Rebuilt Engines: £2,700-£4,500
Mercedes Benz S Class S350
M276 3.5L Petrol
Rebuilt Engines: £2,300-£4,000
Mercedes Benz S Class S450
M256 3.0L MHEV
Rebuilt Engines: £3,200-£5,400
Mercedes Benz S Class S500
M278/M256 4.0L V
Rebuilt Engines: £2,800-£5,100
Mercedes Benz S Class S560
M278 4.0L V
Rebuilt Engines: £3,100-£5,500
Mercedes Benz S Class S65 AMG
M279 6.0L V
Rebuilt Engines: £6,500-£11,500
Mercedes Benz S Class S580e
M256 3.0L PHEV
Rebuilt Engines: £3,800-£6,200
Mercedes Benz S Class S400 Hybrid
M276 3.5L Hybrid
Rebuilt Engines: £2,700-£4,500
Not sure which variant your Mercedes Benz S Class is- Enter your registration number above - we'll identify the exact sub-model, engine code and compatible replacement options instantly.
S Class
Engine Codes
Mercedes Benz S Class Engine CodesFull Technical Specifications & Replacement Guide
Every engine code fitted to the Mercedes Benz S Class across all generations, with technical specs, compatible variants and trims, known failure points, and average rebuilt prices from UK specialists. Select any engine code to compare quotes.
Diesel Engines
Extracted from detailed diesel engine families across Mercedes Benz S Class variants.
OM656 - 3.0L Diesel
Main replacement triggers are timing chain wear, EGR / cooling faults and turbo-control issues.
Compatible variants
S350dS350d 4MATICS400dS400d 4MATIC
Avg. rebuilt price
£2,400 - £4,300
Supply only
Technical specifications
- Fuel type
- Diesel
- Engine size
- 3.0L
- Power output
- 286-340 hp
- Years fitted
- Check by registration
Common failures
- ●Main replacement triggers are timing chain wear, EGR / cooling faults and turbo-control issues.
- ●Confirm exact engine code and fitment before ordering.
- ●Ask for warranty and supply & fit terms.
Not sure which engine code?
Can't find your engine code- Enter your registration number above - we'll instantly identify the exact unit, its technical specifications, and live replacement prices from UK Mercedes Benz S Class engine specialists. Every rebuilt engine comes with a minimum 12-month unlimited mileage warranty.
S Class
Common Problems
Mercedes Benz S Class Engine Problems - What It Costs to Fix & When Replacement Makes Sense
The Mercedes Benz S Class is engineered for flagship longevity, but complex direct-injection systems and advanced hybrid architectures in the M278, OM656 and M256 engine families can lead to costly failures as mileage increases. When components like timing chains, EGR coolers or mild-hybrid control units deteriorate, repair costs often escalate beyond the...
Mercedes Benz S Class OM656 EGR Cooler Cracking - Why Modern BlueTEC Diesel Engines Fail
Mercedes Benz S Class OM656 EGR Cooler Cracking
Most affected vehicles
Mercedes Benz S Class S350dS400d (2017-present
Mercedes Benz S Class S350d, S400d (2017-present, OM656 3.0L inline-6 diesel)
Failure mileage range
60,000 - 90,000 miles
Typical failure window
Root cause
Thermal stress from repeated high-temperature exhaust gas recirculation causes micro-fractures in the integrated EGR cooler matrix, leading to coolant loss and potential hydrolock.
Our recommendation
On a Mercedes Benz S Class S350d or S400d valued at £15,000-£45,000 depending on trim, catching the EGR cooler crack early is financially sensible. However, if the unit has already ingested coolant or suffered hydrolock, partial repair is a false economy. We recommend a complete rebuilt OM656 with reinforced brazing upgrades to eliminate the weak point permanently.
Compare rebuilt OM656 diesel engine prices for your Mercedes Benz S ClassReplacement Engine Options
Mercedes Benz S Class Engine TypesOptions, Costs & What to Expect
Every engine type is available through our UK network with typical price ranges based on variant, engine code and budget.
Mercedes Benz S Class Reconditioned Engines (Recon)£2,800 - £4,500((supply only))
Mercedes Benz S Class Rebuilt Engines£3,200 - £5,200((supply only))
Mercedes Benz S Class Used Engines£1,800 - £3,000((supply only))
Mercedes Benz S Class Remanufactured Engines£5,500 - £8,500((supply only))
Mercedes Benz S Class Refurbished Engines£2,200 - £3,800((supply only))
Compare Mercedes Benz S Class engine prices with vetted UK suppliers
All engine types include a minimum 12-month unlimited mileage warranty when sourced through EngineMarket. Prices are typical UK market ranges based on historical quote data from our network and depend on exact engine code, variant, mileage and supplier. Use our free comparison tool above - enter your registration to get tailored quotes for your specific Mercedes Benz S Class within hours.
Engine Sizes
Mercedes Benz S Class Engines by SizeFind the Right Displacement for Your Variant
Every displacement officially fitted to the Mercedes Benz S Class is detailed below, complete with compatible engine codes, production years, variant compatibility and documented failure points.
The 3.0L inline-6 and V6 diesel units have served as the backbone of the S Class fleet across the W221, W222 and W223 generations. Renowned for strong low-end torque and advanced BlueTEC AdBlue after-treatment, these engines balance flagship refinement with exceptional long-haul efficiency. Their compact architecture and sophisticated common-rail injection make them a preferred choice for UK owners prioritising drivability and economy.
⚙
Engine Code(s)
OM642, OM656
▣
Compatible Models (UK)
S350 CDI (W221, 2005-2013), S350d (W222/W223, 2013-present), S400d
ϟ
Power output
Verified by registration
△
Common Failure Points
EGR cooler matrix cracking, oil cooler seal degradation, turbo actuator wear at higher mileage
Production Years: W222/W223, 2018-present
Get quotes for Mercedes Benz S Class 3.0L diesel enginesMercedes Benz S Class Engines Fuel Type
Mercedes Benz S Class Engines by Fuel Type
Choose your Mercedes Benz S Class engine by fuel type to compare realistic replacement prices, known issues, and compatible UK supply options - from early OM642 diesels to the latest M256 mild-hybrid inline-six.
Mercedes Benz S Class Diesel Engines
DieselDiesel power has defined the S Class fleet across W221, W222 and W223 generations, delivering flagship refinement with BlueTEC efficiency and strong torque for executive long-distance cruising.
Common Mercedes Benz S Class Diesel Engine Families
- •OM656 - inline-6 BlueTEC (S350d/S400d), EGR cooler cracking at 60-90k miles
- •OM642 - V6 CDI legacy unit (S350 CDI), oil cooler seal degradation common
Found In
- •W221 Saloon (2005-2013) - OM642 3.0L V6
- •W222 Saloon (2013-2020) - OM642, OM656 3.0L inline-6
- •W223 Saloon (2020-present) - OM656 3.0L inline-6
Known For
- •Exceptional motorway fuel economy and low-end torque for effortless cruising
- •OM656 EGR cooler matrix fractures causing coolant loss and potential hydrolock
- •OM642 oil cooler seal leaks leading to coolant/oil contamination at higher mileage
Typical Diesel Models
- •S350 CDI
- •S350d
- •S350d 4MATIC
1 of 4
Mercedes Benz S Class Diesel Engines
DieselDiesel power has defined the S Class fleet across W221, W222 and W223 generations, delivering flagship refinement with BlueTEC efficiency and strong torque for executive long-distance cruising.
Common Mercedes Benz S Class Diesel Engine Families
- •OM656 - inline-6 BlueTEC (S350d/S400d), EGR cooler cracking at 60-90k miles
- •OM642 - V6 CDI legacy unit (S350 CDI), oil cooler seal degradation common
Found In
- •W221 Saloon (2005-2013) - OM642 3.0L V6
- •W222 Saloon (2013-2020) - OM642, OM656 3.0L inline-6
- •W223 Saloon (2020-present) - OM656 3.0L inline-6
Known For
- •Exceptional motorway fuel economy and low-end torque for effortless cruising
- •OM656 EGR cooler matrix fractures causing coolant loss and potential hydrolock
- •OM642 oil cooler seal leaks leading to coolant/oil contamination at higher mileage
Typical Diesel Models
- •S350 CDI
- •S350d
- •S350d 4MATIC
Mercedes Benz S Class Petrol Engines
PetrolPetrol S Class variants span naturally aspirated V6 smoothness to hand-built AMG V8 and V12 performance, with direct injection and twin-turbo technology defining modern flagship powertrains.
Common Mercedes Benz S Class Petrol Engine Families
- •M276 - 3.5L V6 (S350/S400 Hybrid), timing chain tensioner wear on early units
- •M278 - 4.0L V8 biturbo (S500/S560), timing chain guide rail degradation
- •M256 - 3.0L inline-6 (S450/S500/S580), mild-hybrid EQ Boost integration
Found In
- •W221 Saloon (2005-2013) - M273, M275, M279
- •W222 Saloon (2013-2020) - M276, M278, M176, M177, M279
- •W223 Saloon (2020-present) - M256, M176, M177
Known For
- •Refined, vibration-free power delivery befitting flagship luxury saloon expectations
- •M278 timing chain guide wear causing cold-start rattles between 70-100k miles
- •M276 hydraulic tensioner failure leading to timing drift on early W222 models
Typical Petrol Models
- •S350
- •S450
- •S500
Mercedes Benz S Class Mild Hybrid (MHEV) Engines
MHEVThe M256 inline-six with 48-volt EQ Boost technology represents the future of S Class petrol efficiency, combining electrified assistance with traditional combustion refinement across W223 models.
Mercedes Benz S Class MHEV Engine Codes
- •M256 E30 DEH LA - 3.0L inline-6 with integrated starter-generator (S450/S500/S580)
- •48-volt belt-driven starter-generator recovers braking energy for electric torque assist
- •EQ Boost provides up to 22hp temporary power boost during acceleration and seamless stop-start
Found In
- •S450, S500, S580 (W223, 2020-present)
Important Notes
- •MHEV engine replacement mandates 48V BSG unit inspection and software recalibration
- •Specialist coordination required for EQ Boost integration and high-voltage safety protocols
- •Availability more limited than standard petrol units; lead times may apply for certified rebuilds
1-3 of 4
Not sure which fuel type your Mercedes Benz S Class has- Enter your registration number above to instantly identify your engine code, fuel system and compatible replacement options - all backed by a minimum 12-month unlimited mileage warranty from UK Mercedes Benz S Class specialists.
Engine YearsGet quotes for 2005-2008 Mercedes Benz S Class replacement engines →
Mercedes Benz S Class Engines by YearWhat Was Fitted & WhenMercedes Benz S Class Engines by Year - What Was Fitted & When
This technical timeline covers every major engine change across the Mercedes Benz S Class production span from 2005 to present, helping owners quickly identify their powertrain and compare rebuilt engine prices from UK specialists.
⚙Key Changes
- ✓Complete platform redesign replacing W220 with double-wishbone front suspension and Airmatic
- ✓Introduction of OM642 3.0L V6 diesel and M272/M273 petrol families for mainstream and flagship trims
- ✓Launch of COMAND APS infotainment, Keyless-Go, and advanced PRE-SAFE crash preparation systems
▣Main Engines
OM642- 3.0L diesel (S350 CDI)
M273- 4.6L/5.5L petrol (S450, S500)
M275- 5.5L twin-turbo petrol (S600)
▰Popular Models
- •Mercedes Benz S350 CDI
- •Mercedes Benz S500
- •Mercedes Benz S600
🔧Known For
- ✓OM642 early production units exhibit oil cooler seal degradation typically between 80k-100k miles
- ✓Robust chassis longevity with exceptional long-term interior material quality
- ✓M275 V12 delivers immense torque but requires specialist servicing for twin-turbo ancillaries
Engine Codes Covered:
OM642M273M275Not sure which year your Mercedes Benz S Class was built- Enter your registration number and we'll identify the exact engine, model year, and compatible replacement options instantly - all backed by a minimum 12-month warranty from UK Mercedes Benz S Class specialists.
FAQ