Mercedes Benz E Class 300 / 450 Modern Petrol Engine ReplacementCompare Prices & Get Quotes
Get quotes today from trusted UK Mercedes Benz E Class 300 and 450 petrol engine specialists. Compare prices on reconditioned, rebuilt and used M274 and M256 engines - including EQ Boost mild-hybrid variants - supply & fit available nationwide.
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12-Month Warranty
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100+ Suppliers
From £3,200 to £8,500
Used from £2,000 · Reconditioned from £3,500 · Common codes: M274.920, M256.930
From £2,000
Tested, bare/short engine
From £3,500
Rod bearings addressed, tested
From quote
Upgraded bearings, full teardown, revised valvetrain
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3 Simple Steps3 Simple Stepsto Finding the Best Mercedes Benz E Class 300 / 450 Modern Petrol Replacement Engineto Finding the Best Mercedes Benz E Class 300 / 450 Modern Petrol Replacement Engine
Most replacements completed within 3-5 days.
Variant HistoryMercedes Benz E Class 300 / 450 Modern Petrol - Engine History & Specs at a Glance
The E 300 and E 450 petrol badges represent Mercedes-Benz's premium petrol offerings across the W213 and W214 E-Class generations. The E 300 uses the M274 2.0-litre turbocharged four-cylinder - a proven but troubled unit - while the E 450 is powered by the M256 3.0-litre turbocharged straight-six, Mercedes' first petrol inline-six since the M104. The M256 introduced EQ Boost mild-hybrid technology, featuring a 48-volt electrical system with an integrated starter-generator (ISG) that adds up to 16 kW (22 hp) and 220 Nm of torque assistance. The M256 is also equipped with an electric auxiliary compressor (BorgWarner eBooster) that spins at up to 70,000 rpm to virtually eliminate turbo lag. The modular engine family shares a 500 cc per cylinder architecture with Mercedes' four-cylinder and V8 engines.
Variant HistoryMercedes Benz E Class 300 / 450 Modern Petrol - Engine History & Specs at a Glance
The E 300 and E 450 petrol badges represent Mercedes-Benz's premium petrol offerings across the W213 and W214 E-Class generations. The E 300 uses the M274 2.0-litre turbocharged four-cylinder - a proven but troubled unit - while the E 450 is powered by the M256 3.0-litre turbocharged straight-six, Mercedes' first petrol inline-six since the M104. The M256 introduced EQ Boost mild-hybrid technology, featuring a 48-volt electrical system with an integrated starter-generator (ISG) that adds up to 16 kW (22 hp) and 220 Nm of torque assistance. The M256 is also equipped with an electric auxiliary compressor (BorgWarner eBooster) that spins at up to 70,000 rpm to virtually eliminate turbo lag. The modular engine family shares a 500 cc per cylinder architecture with Mercedes' four-cylinder and V8 engines.
Mercedes Benz E Class 300 / 450 Modern Petrol
Fuel TypePetrol (Turbocharged Direct Injection with Mild Hybrid - EQ Boost)
Engine Size Range2.0L (E 300) - 3.0L (E 450)
Power Output Range180 kW (245 hp) - 270 kW (367 hp) (+ EQ Boost assistance)Engine History Timeline
**2016** - W213 E 300 launched with M274.920 2.0-litre turbo four-cylinder 180 kW (245 hp), 370 Nm
**2017** - M256 engine introduced on W222 S-Class later adopted by E-Class range
**2018** - E 450 launched with M256.930 3.0-litre straight-six 270 kW (367 hp), 500 Nm, featuring EQ Boost mild-hybrid system
**2018-2020** - E 400 (pre-facelift) offered with M276 V6 in some markets superseded by E 450
**2020** - W213 facelift; E 300 continues with M274 E 450 gains updated M256.930 with enhanced mild-hybrid system
**2020** - E 450 EQ Boost 4MATIC introduced with 367 hp and 500 Nm
**2023** - W214 generation launched; E 300 and E 450 continue with updated M256/M254 engine architecture
Key Specs Snapshot
Fuel TypePetrol (Turbocharged Direct Injection with Mild Hybrid - EQ Boost)Engine Size Range2.0L (E 300) - 3.0L (E 450)Power Output Range180 kW (245 hp) - 270 kW (367 hp) (+ EQ Boost assistance)Torque Range370 Nm - 500 NmYears Produced2016-presentEvery engine fitted to the Mercedes E Class 300 and 450 modern petrol is covered below, with UK rebuilt pricing and known failure points.
Mercedes Benz E Class 300 / 450 Modern Petrol Engine Codes - Specifications & Replacement CostMercedes Benz E Class 300 / 450 Modern Petrol Engine Codes - Specifications & Replacement Cost
2.0L Turbo Petrol (2016-2021)
Power Output180 kW (245 hp) at 5,500 rpmTorque370 Nm at 1,300-4,000 rpmYears Fitted2016-2021 (W213 E-Class)
Compatible Trim Levels
- E 300 (W213)
- E 300 AMG Line
- E 300 Exclusive
- E 300 4MATIC (select markets)
Mercedes Benz E Class 300 / 450 Modern Petrol engine replacement
Find your exact engine code, specs and UK replacement cost guide.
Used
Tested, ready-to-fit engine
£2,000-£3,200
Reconditioned
Addressed known issues, tested
£3,200-£4,800
Rebuilt
Full teardown, upgraded internals
£3,800-£5,500
Common Failure
Piston cracking from low-speed pre-ignition (LSPI) is a catastrophic and well-documented failure on the M274. Timing chain stretch and thermostat failure are also common. The M274 in the E 300 shares the same fundamental weaknesses as the E 200 and E 250 variants - there is no preventative fix for piston cracking beyond engine replacement.
The E Class 300 and 450 represent the pinnacle of Mercedes petrol engineering in the modern era. The M274 four-cylinder in the E 300 is a powerful unit but carries a catastrophic reputation for piston cracking - a failure with no preventative fix. The M256 straight-six in the E 450 is a technological marvel - Mercedes' first petrol inline-six since the M104 - featuring EQ Boost mild-hybrid technology, but it introduces its own set of complex issues around timing chain wear and 48-volt system reliability. Every rebuilt engine supplied through EnginesMarket includes upgraded components designed to address the original failure point, plus a minimum 12-month unlimited mileage warranty. Below, we break down what these failures cost to fix and when replacement is the smarter option.
The E 300 Catastrophic Failure
Affected Vehicles
Mercedes E Class 300 (M274.920, 2016-2021)
Typical Failure Mileage
30,000 - 90,000 miles (some as early as 40,000 miles)
Root Cause
Low-speed pre-ignition (LSPI) combined with oil dilution causes detonation events that crack pistons between ring lands. There is no preventative fix - once a piston cracks, the engine must be rebuilt or replaced. The M274 piston failure is so well-documented that some owners have been advised to "dump the E300" rather than repair it, as a repaired engine remains as prone to cracking as the original.
Why It Happens
Low-speed pre-ignition (LSPI) combined with oil dilution causes detonation events that crack pistons between ring lands. There is no preventative fix - once a piston cracks, the engine must be rebuilt or replaced. The M274 piston failure is so well-documented that some owners have been advised to "dump the E300" rather than repair it, as a repaired engine remains as prone to cracking as the original.
Dealer (parts + labour)
£5,000-£7,000
Specialist (parts + labour)
£3,500-£5,000
What it involves
New or reconditioned short block fitted with existing ancillaries
Suitability
30,000-90,000 miles; cranks and pistons new, head reused
1 - 2 daysDealer (parts + labour)
£6,500-£9,000
Specialist (parts + labour)
£3,800-£5,500
What it involves
Supply & fit of fully rebuilt M274 with forged pistons and upgraded rings
Suitability
Prevents repeat failure; the only permanent solution
1 - 2 daysDealer (parts + labour)
£4,000-£5,500
Specialist (parts + labour)
£2,800-£4,000
What it involves
Supply & fit of low-mileage used M274 from salvage
Suitability
Same design flaw remains - no upgrade, same risk
1 - 2 daysAll prices are indicative UK market ranges based on current UK specialist supplier data.| Repair Tier | Dealer (Parts + Labour) | Specialist (Parts + Labour) | What It Involves | Suitability | Estimated Time |
|---|---|---|---|---|---|
 Major - Short Block Replacement Minor | £5,000-£7,000 | £3,500-£5,000 | New or reconditioned short block fitted with existing ancillaries | 30,000-90,000 miles; cranks and pistons new, head reused | 1 - 2 days |
 Full Replacement - Rebuilt Engine with Forged Pistons Best Value | £6,500-£9,000 | £3,800-£5,500 | Supply & fit of fully rebuilt M274 with forged pistons and upgraded rings | Prevents repeat failure; the only permanent solution | 1 - 2 days |
Replacement - Used Engine Best Value | £4,000-£5,500 | £2,800-£4,000 | Supply & fit of low-mileage used M274 from salvage | Same design flaw remains - no upgrade, same risk | 1 - 2 days |
Vehicle Value Check
Vehicle Value Check
A typical W213 E 300 is worth £10,000-£22,000 depending on condition and mileage【INDUSTRY ESTIMATE】. Given the high residual value, a specialist-supplied rebuilt engine with forged pistons is the clear choice - it costs marginally more than a used replacement but eliminates the repeat failure risk. Avoid dealer pricing here - the premium buys no design improvement.
Our Recommendation
Our Recommendation
There is no minor repair for a cracked piston - the engine must come apart. On a W213 E 300 worth £10,000+, a specialist-supplied rebuilt engine with forged pistons is the only sensible long-term solution. The M274's piston cracking is a design weakness that used engines do not address - only a rebuilt unit with upgraded pistons eliminates the repeat failure risk. If you're considering a used E 300 purchase, factor a £3,800-£5,500 engine replacement into your budget - many owners have been caught out by this failure.
Don't Let Engine Failure Write Off Your Mercedes E Class 300 or 450 Modern Petrol
Whether your E Class 300 is suffering from piston failure or timing chain rattle, or your E 450 is experiencing cold-start timing chain noise or oil consumption issues, EnginesMarket makes it simple to compare prices from trusted UK Mercedes specialists. Every rebuilt engine in our network includes upgraded components designed to address the original failure point - plus a minimum 12-month unlimited mileage warranty and nationwide delivery. Compare prices, choose a specialist, and get back on the road without the main dealer premium.
Compare rebuilt M274 Mercedes E Class 300 petrol engine prices
12-Month Minimum
UK Specialists Vetted
Best Price GuidanceImportant Information
Important Information
"All prices are indicative UK market ranges based on historical quote data and repair requests from our network of engine specialists. Dealer pricing is estimated based on published main dealer labour rates and genuine OEM parts pricing. Specialist pricing reflects actual quote data from EnginesMarket's UK network. Actual costs vary depending on damage severity, vehicle condition, variant, and workshop location within the UK. Use our free comparison tool to get tailored quotes for your specific Mercedes E Class 300 or 450 modern petrol. Every engine supplied through EnginesMarket carries a minimum 12-month unlimited mileage warranty - always confirm exact terms with your chosen supplier."
Mercedes E Class 300 / 450 Modern Petrol Engine ReplacementFrequently Asked Questions
Question 1How much does a Mercedes E Class 450 engine replacement cost in the UK-
Short summary: Supply-only rebuilt M256 engines range from £5,500 to £8,500 depending on condition. With specialist fitting, budget £6,000-£9,300 total.
- M274.920 (E 300, 245 hp, 2016-2021): rebuilt £3,800-£5,500
- M256.930 (E 450, 367 hp with EQ Boost, 2018-present): rebuilt £5,500-£8,500
- Labour adds £500-£1,000 depending on specialist location - the M256's rear-mounted timing chain makes it a more complex job
Question 2What are the signs of M274 piston failure in an E Class 300-
Short summary: There are often no warning signs - the M274's piston cracking from LSPI is sudden and catastrophic. Some owners report a knocking noise or loss of power immediately before failure.
- Loss of power or engine misfire
- Knocking noise from the engine
- Check engine light with misfire codes
- There is no preventative fix - rebuilt engines with forged pistons are the only permanent solution
Question 3Is it worth replacing the engine on an E Class 300 or 450-
Short summary: Yes, if the car is otherwise sound. W213 E 300 examples command £10,000-£22,000 used, while E 450 examples command £20,000-£40,000, making replacement viable【INDUSTRY ESTIMATE】.
- A quality rebuilt M274 costs £3,800-£5,500 supply only
- A quality rebuilt M256 costs £5,500-£8,500 supply only
- The M256 is Mercedes' most advanced straight-six petrol engine
- A replacement engine with warranty costs less than the depreciation on a newer car
Question 4What causes the M256 timing chain to fail on E 450 models-
Short summary: The M256's timing chain tensioners and guides can wear prematurely, causing cold-start rattling - described as "marbles in a can". M256 engines can show timing component wear after 120,000 km.
- Timing chain rattle typically occurs between 40,000-75,000 miles
- Cold-start rattling that disappears after a few seconds is the early warning
- The timing chain is located at the rear of the engine - replacement is an engine-out job
- Full timing chain replacement at a specialist costs £2,200-£3,500
Question 5What is the difference between the M274 and M256 engines in the E Class-
Short summary: The M274 is a 2.0-litre turbocharged four-cylinder (E 300, 245 hp) with known piston cracking issues. The M256 is a 3.0-litre turbocharged straight-six (E 450, 367 hp) with EQ Boost mild-hybrid technology - more powerful, smoother, and generally more reliable.
- M274: 2.0L four-cylinder, 245 hp, 370 Nm - prone to piston cracking, timing chain stretch, and thermostat failure
- M256: 3.0L straight-six, 367 hp + 22 hp EQ Boost, 500 Nm - features 48-volt mild-hybrid system, electric auxiliary compressor, and integrated starter-generator
- The M256 replaced the M276 V6 and is Mercedes' first petrol straight-six since the M104
- The M256 is generally more reliable but more expensive to repair due to complexity
Question 6How long does a Mercedes E Class 450 engine last-
Short summary: With proper maintenance and 8,000-10,000 mile oil changes, M256 engines regularly reach 150,000-200,000+ miles. The M256 is a modern, efficient design with a robust bottom end.
- M256 straight-six is a modular design sharing architecture with four-cylinder and V8 engines
- Timing chain inspection/replacement at 40k-75k miles is recommended if rattle occurs
- Regular oil changes (8,000 miles) are critical for timing chain life
- The M256 is generally considered more reliable than the M274
Why Choose UsCompare Mercedes E Class 300 / 450 Modern PetrolEngine PricesToday
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