How much does a Mercedes R231 engine replacement cost in the UK?

A reconditioned R231 engine typically costs £2,500–£14,000 supply only, depending on the engine — the M276 V6 sits at £2,500–£6,000, while the M278 V8 is £3,500–£7,500, the M157 AMG V8 is £5,000–£9,000, and the V12 M279 is £8,000–£14,000. Fitting adds £650–£1,500 depending on the variant. Use our calculator for a personalised quote.

Which R231 engine is the most reliable?

The M276 V6 (SL 350/SL 400) is the most reliable choice — it's Mercedes-developed, refined, and has a strong track record when serviced properly. The M157 AMG V8 (SL 63 AMG) is also reliable, though owners should watch for wiring harness oil intrusion. The M278 V8 (SL 500) is the least reliable of the mainstream engines.

What are the common problems with the R231?

The M278 V8 (SL 500) is known for cylinder scoring and oil/coolant leaks; early M276 V6 engines (pre-2014) can suffer from timing chain tensioner issues; and the M157 AMG V8 can develop oil intrusion into the wiring harness. Engine and transmission mounts are also known to wear prematurely. Regular servicing is key.

Is the Mercedes R231 reliable overall?

Yes — the R231 is generally regarded as one of the most reliable SL generations, especially with the M276 V6 and M157 AMG V8 engines. The M278 V8 requires more careful maintenance. The V12 M279 is reliable but exceptionally expensive to service. All engines benefit from regular, attentive servicing.

Which R231 engine should I avoid?

The M278 V8 (SL 500) — its cylinder scoring issues can lead to catastrophic engine failure, and the fix is very expensive. Some owners have found that excessively long service intervals are partly to blame. If you're considering an SL 500, have a specialist inspect the engine thoroughly and verify the service history. The M279 V12 (SL 65 AMG) is not an engine to avoid, but buyers should be aware of the astronomical running costs.

How do I know if my R231 engine needs replacing?

Warning signs include excessive oil consumption and blue smoke (M278 cylinder scoring), rattling noise on cold start (M276 timing chain), check engine light with wiring harness faults (M157 oil intrusion), or excessive vibration (engine mounts). If you notice any of these, have the car inspected immediately — ignoring them can lead to a full engine failure.

How long do Mercedes R231 engines last?

The M276 V6 can easily exceed 100,000 miles with regular servicing. The M157 AMG V8 is similarly durable with proper maintenance. The M278 V8 has a shorter lifespan if cylinder scoring develops, though careful maintenance can mitigate the risk. The M279 V12 is reliable but demands meticulous maintenance.

What is the difference between the R231 and the previous R230?

The R231 is the sixth-generation SL, built on an all-aluminium space-frame bodyshell that's 140 kg lighter than the R230. It introduced new engines including the M276 V6, M278 V8, and M157 AMG V8. The R230 (2001–2012) used older M112, M113, M272, and M273 engines and is covered on its own generation page.

How do I find my Mercedes R231 engine code?

The engine code is on the VIN plate (visible through the windscreen), on the vehicle documentation, and stamped on the engine block. For the R231, common codes are M276 (V6 petrol), M278 (V8 petrol), M157 (AMG V8), and M279 (AMG V12). Tell us your variant and year, and we'll identify it — 25+ vetted Mercedes specialists will confirm it for free.

R231 Engine Replacement Cost UK

Name: Mercedes SL R231 UK Engine Enquiry Data 2025
Creator: MercedesEngines.uk

Mercedes SL R231 Engine Codes — The Complete Database

Every engine fitted to the R231 specifically — including the pre- and post-facelift changes that introduced the SL 400 and updated power outputs.

Engine CodeFamilyFuelDisplacementPowerYears (R231)Variants (badges)Reliability2025 EnquiriesAvg. Recon Cost

M276.954M276Petrol, V63.5L (3498cc)306 bhp2012–2014SL 350★★★★☆ [PROVISIONAL — well-regarded M276 V6; some pre-2014 tensioner issues]390 [MB-VERIFIED]£2,500–£5,000 [MB-QUOTE]

M276.825M276Petrol, twin-turbo V63.0L (2996cc)333 bhp2014–2016SL 400★★★★☆ [PROVISIONAL — bi-turbo M276; strong and reliable]390 [MB-VERIFIED]£2,800–£5,500 [MB-QUOTE]

M276.825 (facelift)M276Petrol, twin-turbo V63.0L (2996cc)367 bhp2016–2020SL 400 (facelift)★★★★☆ [PROVISIONAL — upgraded bi-turbo; 35 hp gain]390 [MB-VERIFIED]£3,000–£6,000 [MB-QUOTE]

M278.927M278Petrol, twin-turbo V84.7L (4663cc)435 bhp2012–2014SL 500★★★☆☆ [PROVISIONAL — known for cylinder scoring and oil leaks]— (pattern data)£3,500–£7,000 [MB-QUOTE]

M278.927 (facelift)M278Petrol, twin-turbo V84.7L (4663cc)455 bhp2015–2020SL 500 (facelift)★★★☆☆ [PROVISIONAL — updated M278; same cylinder scoring concerns]— (pattern data)£3,800–£7,500 [MB-QUOTE]

M157.983M157Petrol, twin-turbo V85.5L (5461cc)537–585 bhp2012–2020SL 63 AMG★★★★☆ [PROVISIONAL — robust AMG V8; watch for oil intrusion in wiring harness]370 [MB-VERIFIED]£5,000–£9,000 [MB-QUOTE]

M279.981M279Petrol, twin-turbo V126.0L (5980cc)630 bhp2012–2020SL 65 AMG★★★☆☆ [PROVISIONAL — AMG V12; complex and costly to maintain]— (pattern data)£8,000–£14,000 [MB-QUOTE]

Engine CodeFuelPowerYearsReliabilityEnquiriesAvg. Recon Cost

M276.954M276Petrol, V6306 bhp2012–2014★★★★☆ [PROVISIONAL — well-regarded M276 V6; some pre-2014 tensioner issues]390 [MB-VERIFIED]£2,500–£5,000 [MB-QUOTE]

M276.825M276Petrol, twin-turbo V6333 bhp2014–2016★★★★☆ [PROVISIONAL — bi-turbo M276; strong and reliable]390 [MB-VERIFIED]£2,800–£5,500 [MB-QUOTE]

M276.825 (facelift)M276Petrol, twin-turbo V6367 bhp2016–2020★★★★☆ [PROVISIONAL — upgraded bi-turbo; 35 hp gain]390 [MB-VERIFIED]£3,000–£6,000 [MB-QUOTE]

M278.927M278Petrol, twin-turbo V8435 bhp2012–2014★★★☆☆ [PROVISIONAL — known for cylinder scoring and oil leaks]— (pattern data)£3,500–£7,000 [MB-QUOTE]

M278.927 (facelift)M278Petrol, twin-turbo V8455 bhp2015–2020★★★☆☆ [PROVISIONAL — updated M278; same cylinder scoring concerns]— (pattern data)£3,800–£7,500 [MB-QUOTE]

M157.983M157Petrol, twin-turbo V8537–585 bhp2012–2020★★★★☆ [PROVISIONAL — robust AMG V8; watch for oil intrusion in wiring harness]370 [MB-VERIFIED]£5,000–£9,000 [MB-QUOTE]

M279.981M279Petrol, twin-turbo V12630 bhp2012–2020★★★☆☆ [PROVISIONAL — AMG V12; complex and costly to maintain]— (pattern data)£8,000–£14,000 [MB-QUOTE]

Overview

Mercedes SL R231 — Overview

The R231 is the sixth generation of the Mercedes‑Benz SL‑Class, a two‑seat grand tourer roadster launched in March 2012 as the successor to the R230.

Built on an all‑aluminium space‑frame bodyshell, it was 140 kg lighter than its predecessor and offered a 20 per cent increase in torsional rigidity. The engine range spanned from the 3.5‑litre M276 V6 to the 4.7‑litre M278 V8, with AMG variants delivering up to 630 bhp from the M279 V12. A significant facelift arrived in 2016, bringing power upgrades and refreshed styling. Production ended in 2020, succeeded by the Mercedes‑AMG R232.

Key Facts

Platform

Mercedes R231 (all‑aluminium space‑frame)

Predecessor

R230 (2001–2012)

Successor

R232 (2021–present)

Sibling body styles in this generation

none (SL is standalone roadster)

Market Intelligence

The R231 SL generated 880+ real UK engine enquiries in 2025 [MB‑VERIFIED], concentrated on the M276 V6 and M157 AMG V8 as the most‑requested powertrains.

Mercedes SL R231 — Overview

The R231 is the sixth generation of the Mercedes‑Benz SL‑Class, a two‑seat grand tourer roadster launched in March 2012 as the successor to the R230.

Built on an all‑aluminium space‑frame bodyshell, it was 140 kg lighter than its predecessor and offered a 20 per cent increase in torsional rigidity. The engine range spanned from the 3.5‑litre M276 V6 to the 4.7‑litre M278 V8, with AMG variants delivering up to 630 bhp from the M279 V12. A significant facelift arrived in 2016, bringing power upgrades and refreshed styling. Production ended in 2020, succeeded by the Mercedes‑AMG R232.

Key Facts

Platform

Mercedes R231 (all‑aluminium space‑frame)

Predecessor

R230 (2001–2012)

Successor

R232 (2021–present)

Sibling body styles in this generation

none (SL is standalone roadster)

Market Intelligence

The R231 SL generated 880+ real UK engine enquiries in 2025 [MB‑VERIFIED], concentrated on the M276 V6 and M157 AMG V8 as the most‑requested powertrains.

Best & Worst Engines

Best Petrol Overall

M276.825 (SL 400, facelift)

“Mercedes' 3.0‑litre bi‑turbo V6, upgraded to 367 bhp in the 2016 facelift, delivers effortless performance with 500 Nm of torque. It's the sweet spot in the R231 range — refined, responsive, and considerably more reliable than the V8 alternatives.”

Who it's for: buyers who want grand touring performance without the V8's running costs or reliability concerns.

Highest Risk

M278.927 (SL 500)

“The 4.7‑litre bi‑turbo V8 is known for cylinder scoring and coolant/oil leaks. While it delivers effortless power, these issues can be costly to address. The M278 is widely considered the most problematic engine in the R231 range.”

Who it's for: buyers who prioritise V8 presence and are prepared for potentially expensive maintenance.

Most Expensive Failure

M279.981 (SL 65 AMG) — V12 complexity

“The 6.0‑litre twin‑turbo V12 is a masterpiece of engineering but exceptionally complex and costly to maintain. Parts are expensive, labour is intensive, and specialist knowledge is required.”

Who it's for: collectors and enthusiasts who want flagship V12 status and can afford the premium running costs.

Best Value

M276.954 (SL 350)

“The 3.5‑litre naturally aspirated V6 offers the best balance of performance (306 bhp), characterful engine note, and reliability. It's the most affordable entry point into R231 ownership.”

Who it's for: buyers who want the SL experience without the turbocharged complexity.

Most Overlooked

M157.983 (SL 63 AMG)

“The 5.5‑litre twin‑turbo V8 delivers 537–585 bhp with genuine AMG character. It's often overlooked in favour of the V12 but offers a more engaging and reliable driving experience — watch for oil intrusion in the wiring harness.”

Who it's for: buyers who want AMG performance without the V12's reliability headaches.

Best Petrol Overall

M276.825 (SL 400, facelift)

“Mercedes' 3.0‑litre bi‑turbo V6, upgraded to 367 bhp in the 2016 facelift, delivers effortless performance with 500 Nm of torque. It's the sweet spot in the R231 range — refined, responsive, and considerably more reliable than the V8 alternatives.”

Who it's for: buyers who want grand touring performance without the V8's running costs or reliability concerns.

Highest Risk

M278.927 (SL 500)

“The 4.7‑litre bi‑turbo V8 is known for cylinder scoring and coolant/oil leaks. While it delivers effortless power, these issues can be costly to address. The M278 is widely considered the most problematic engine in the R231 range.”

Who it's for: buyers who prioritise V8 presence and are prepared for potentially expensive maintenance.

Most Expensive Failure

M279.981 (SL 65 AMG) — V12 complexity

“The 6.0‑litre twin‑turbo V12 is a masterpiece of engineering but exceptionally complex and costly to maintain. Parts are expensive, labour is intensive, and specialist knowledge is required.”

Who it's for: collectors and enthusiasts who want flagship V12 status and can afford the premium running costs.

Best Value

M276.954 (SL 350)

“The 3.5‑litre naturally aspirated V6 offers the best balance of performance (306 bhp), characterful engine note, and reliability. It's the most affordable entry point into R231 ownership.”

Who it's for: buyers who want the SL experience without the turbocharged complexity.

Most Overlooked

M157.983 (SL 63 AMG)

“The 5.5‑litre twin‑turbo V8 delivers 537–585 bhp with genuine AMG character. It's often overlooked in favour of the V12 but offers a more engaging and reliable driving experience — watch for oil intrusion in the wiring harness.”

Who it's for: buyers who want AMG performance without the V12's reliability headaches.

Mercedes SL R231 — Ownership Economics

EngineTypical MileageCommon Major FailureRepair Cost (Specialist)Replacement Cost (Recon)Ownership Verdict

M276.954 (SL 350)40k–80kPre‑2014 tensioner issues, chain rattle£500–£1,200£2,500–£5,000

Best Value — reliable, characterful V6.

M276.825 (SL 400)40k–80kChain rattle (early cars), coolant leaks£500–£1,200£2,800–£6,000

Best Petrol — turbocharged refinement.

M278.927 (SL 500)30k–60kCylinder scoring, oil/coolant leaks£1,000–£3,000£3,500–£7,500

Risk vs Reward — powerful but potentially expensive.

M157.983 (SL 63 AMG)30k–60kOil intrusion in wiring harness, engine mounts£800–£2,000£5,000–£9,000

AMG Sweet Spot — reliable V8 with manageable issues.

M279.981 (SL 65 AMG)20k–40kV12 complexity, cooling system, ignition coils£2,000–£5,000£8,000–£14,000

Flagship Tax — exceptional but expensive to maintain.

EngineTypical MileageCommon Major FailureRepair Cost (Specialist)Replacement Cost (Recon)Ownership Verdict

M276.954 (SL 350)40k–80kPre‑2014 tensioner issues, chain rattle£500–£1,200£2,500–£5,000

Best Value — reliable, characterful V6.

M276.825 (SL 400)40k–80kChain rattle (early cars), coolant leaks£500–£1,200£2,800–£6,000

Best Petrol — turbocharged refinement.

M278.927 (SL 500)30k–60kCylinder scoring, oil/coolant leaks£1,000–£3,000£3,500–£7,500

Risk vs Reward — powerful but potentially expensive.

M157.983 (SL 63 AMG)30k–60kOil intrusion in wiring harness, engine mounts£800–£2,000£5,000–£9,000

AMG Sweet Spot — reliable V8 with manageable issues.

M279.981 (SL 65 AMG)20k–40kV12 complexity, cooling system, ignition coils£2,000–£5,000£8,000–£14,000

Flagship Tax — exceptional but expensive to maintain.

The R231 rule

A £2,800–£6,000 M276 recon against a £15,000–£45,000 R231 sits at 6–40% of the car's value — comfortably within our 70% Mercedes threshold, making replacement a sensible decision. Against a higher‑mileage SL 500 with the M278, the same maths is still favourable (8–50%). The R231's strong retained values make most engine replacements economically viable. V12 cars are a different proposition — their replacement costs often approach or exceed the vehicle's value.

Key Takeaways

Which R231 Costs Least To Own?
SL 350 (M276.954) — best balance of performance and reliability.
Which R231 Costs Most To Own?
SL 65 AMG (M279) — V12 running costs are astronomical.
Which R231 Is Best Value?
SL 400 (M276.825) — the sweet spot in the range.

Common Problems

01

M278

V8 Cylinder Scoring & Oil Leaks (SL 500)

Affected models:

SL 500 (M278.927, 2012–2020)

M278 V8 Cylinder Scoring & Oil Leaks (SL 500)

Typical failure mileage:

30,000–60,000 miles

Root cause:

The M278 V8 is known for cylinder scoring (bore wear) and oil/coolant leaks. Regular oil changes using Mercedes‑spec 229.5 oil are critical to mitigate these issues. Camshaft position sensors can also leak oil into the wiring harness.

Tiered Cost Table

Our Recommendation

On SL 500 models, adhere strictly to 5,000‑mile oil change intervals and use only Mercedes‑spec 229.5 oil — an £800–£1,500 preventative repair is far cheaper than the £3,500–£7,500 replacement that follows if cylinder scoring progresses.

Compare M278 engine prices for your R231 SL 500

02

M276

Timing Chain Tensioner Issues (early cars)

Affected models:

SL 350, SL 400 (M276, pre‑2014)

M276 Timing Chain Tensioner Issues (early cars)

Typical failure mileage:

40,000–80,000 miles

Root cause:

Some pre‑2014 M276 engines suffered from timing chain tensioner issues, causing rattling on cold start, check engine lights, and fault codes. Mercedes introduced improved parts after this date.

Tiered Cost Table

Our Recommendation

If you hear a rattling noise on cold start from a pre‑2014 SL 350 or SL 400, have the timing chain tensioner inspected immediately — a £600–£1,200 repair is far cheaper than the £2,500–£5,000 replacement that follows if the chain fails.

Compare M276 engine prices for your R231 V6

03

M157

AMG Wiring Harness Oil Intrusion (SL 63 AMG)

Affected models:

SL 63 AMG (M157.983)

M157 AMG Wiring Harness Oil Intrusion (SL 63 AMG)

Typical failure mileage:

30,000–60,000 miles

Root cause:

The M157 V8 can suffer from oil intrusion into the engine wiring harness, particularly from camshaft position sensors. This can lead to electrical faults, check engine lights, and potential engine damage if not addressed.

Tiered Cost Table

Our Recommendation

On SL 63 AMG models, have the wiring harness and cam sensors inspected at every service — a £600–£1,200 repair is far cheaper than the £4,000–£7,000 replacement that follows if oil contamination causes a major electrical failure.

Compare M157 engine prices for your R231 SL 63 AMG

04

Engine

& Transmission Mount Failure

Affected models:

All R231 variants

Typical failure mileage:

20,000–40,000 miles

Root cause:

The R231's engine and transmission mounts can fail prematurely, leading to excessive movement and vibration. This is particularly noticeable when shifting between drive and reverse.

Tiered Cost Table

Our Recommendation

Have the engine and transmission mounts inspected at every service — a £300–£600 repair is a minor expense compared to the cost of more serious drivetrain issues.

Compare R231 engine mount replacement prices

R231 Engine Replacement Costs — By Engine and Condition

VariantEngine CodeUsed (Supply)Reconditioned (Supply)Rebuilt (Supply)Labour Hours

SL 350M276.954£1,200–£2,500£2,500–£5,000£4,000–£6,50010–14 hrs

SL 400 (pre‑facelift)M276.825£1,500–£2,800£2,800–£5,500£4,500–£7,00010–14 hrs

SL 400 (facelift)M276.825£1,800–£3,200£3,000–£6,000£4,800–£7,50010–14 hrs

SL 500 (pre‑facelift)M278.927£2,000–£3,500£3,500–£7,000£5,500–£8,50012–16 hrs

SL 500 (facelift)M278.927£2,200–£3,800£3,800–£7,500£6,000–£9,00012–16 hrs

SL 63 AMGM157.983£3,000–£5,000£5,000–£9,000£7,000–£11,00014–18 hrs

SL 65 AMGM279.981£5,000–£8,000£8,000–£14,000£10,000–£16,00018–24 hrs

No Generation variance from the Model Page's baseline figures — the R231 is a standalone model with no direct platform‑sharing for engine bay access, so labour times are specific to this generation. Costs are inherited directly per the Authority Model, with no divergence note required.

Core Variants

Petrol Variants

SL 350SL 400SL 500SL 63 AMGSL 65 AMG

Scope note: All variants listed are R231 sixth‑generation SL only. The R231 was not available with a non‑AMG V12 — the SL 600 was discontinued. The SL 400 replaced the SL 350 from November 2014, and the facelift in 2016 brought power upgrades to both the SL 400 (367 bhp) and SL 500 (455 bhp).

Core Variants

Petrol Variants

SL 350SL 400SL 500SL 63 AMGSL 65 AMG

Scope note: All variants listed are R231 sixth‑generation SL only. The R231 was not available with a non‑AMG V12 — the SL 600 was discontinued. The SL 400 replaced the SL 350 from November 2014, and the facelift in 2016 brought power upgrades to both the SL 400 (367 bhp) and SL 500 (455 bhp).

Market Intelligence

Most Requested E90 Engines (2025)

1.1. M276 (V6 petrol) — most‑requested across the Mercedes range [MB‑VERIFIED]
2.2. M157 (5.5 AMG V8) — strong enthusiast demand for the SL 63
3.3. M278 (4.7 V8) — demand for the SL 500

Most Requested E90 Variants

1.1. SL 400
2.2. SL 63 AMG
3.3. SL 500

Average E90 Replacement Cost

£2,500–£14,000 supply only [MB‑QUOTE]

Most Common E90 Failures

1.1. M278 cylinder scoring (SL 500)
2.2. M276 timing chain tensioner (early cars)
3.3. M157 wiring harness oil intrusion (SL 63 AMG)

Live Feed

VehicleLocationIssueEnquiries

Mercedes SL 400 R231 (M276)

London

Rattling noise on cold start, timing chain tensioner suspect

4

enquiries

Mercedes SL 500 R231 (M278)

Birmingham

Oil leak from camshaft sensors, suspected wiring harness contamination

3

enquiries

Mercedes SL 63 AMG R231 (M157)

Manchester

Check engine light, wiring harness oil intrusion

2

enquiries

Updated Monthly

FAQ

BMW 3 Series E90 rear three-quarter view

Why UK Mercedes R231 Owners Trust MercedesEngines.uk

Trusted R231 Engine Suppliers
every garage and engine rebuilder in our network is vetted, rated, and reviewed by real Mercedes owners, as part of the Engine Finders network.
Compare R231 Engine Replacement Companies
see prices, warranty terms, and supply & fit options side‑by‑side before you commit.
UK Engine Replacement Services for R231
covering every variant from SL 350 to SL 65 AMG, with supply‑only or full supply & fit available nationwide.

Find the best Mercedes R231 engine replacement UK drivers rely on. Compare real prices from trusted specialists on EnginesMarket today and get back on the road with confidence.

Compare Mercedes SL R231 Engine Prices on EnginesMarket

Why UK Mercedes R231 Owners Trust MercedesEngines.uk

Trusted R231 Engine Suppliers
every garage and engine rebuilder in our network is vetted, rated, and reviewed by real Mercedes owners, as part of the Engine Finders network.
Compare R231 Engine Replacement Companies
see prices, warranty terms, and supply & fit options side‑by‑side before you commit.
UK Engine Replacement Services for R231
covering every variant from SL 350 to SL 65 AMG, with supply‑only or full supply & fit available nationwide.

Find the best Mercedes R231 engine replacement UK drivers rely on. Compare real prices from trusted specialists on EnginesMarket today and get back on the road with confidence.

Compare Mercedes SL R231 Engine Prices on EnginesMarket

Mercedes SL R231 Engines — The Complete UK Guide

Mercedes SL R231 Engine Codes — The Complete Database

Mercedes SL R231 — Overview

Mercedes SL R231 — Overview

Best & Worst Engines

Mercedes SL R231 — Ownership Economics

Common Problems

R231 Engine Replacement Costs — By Engine and Condition

Core Variants

Core Variants

Market Intelligence

FAQ

Why UK Mercedes R231 Owners Trust MercedesEngines.uk

Why UK Mercedes R231 Owners Trust MercedesEngines.uk