Mercedes-BenzS-Class1991–Present7 Generations • OM642 • OM651 • M276 • OM654 • M177

S-Class Engines — The Complete UK Guide

Every S-Class generation from the W140 to the W223 — engine codes, known failures, replacement costs, and honest economics. Backed by 2,400+ real UK S-Class engine enquiries in 2025 [MB-VERIFIED].

Explore S-Class Engines

  • 2,400+ Enquiries (2025) [MB-VERIFIED]

  • 7 Generations Covered

  • 5 Engine Codes

  • Part of Engine Finders

S-Class —
The Ownership Verdict

Verdict MetricOur Call
Overall Ownership Rating

★★★★☆

Replacement Economics

✅ The S-Class rule: same engine, completely different economics — your generation decides your fate.

Reliability

★★★☆☆ (pre-2013) / ★★★★☆ (2013+)

Most Reliable Engine

OM654 — the modern diesel with the cleanest record in our data [MB-VERIFIED]

Highest-Risk Engine

OM642 — oil cooler seal failure, labour-intensive but rarely terminal; M276 — timing chain stretch on earlier examples

Best Used Buy

W222 (2013–2020) with OM654 or M276 — the high-water mark of S-Class build quality, before the W223's touchscreen-everything interior

Average Engine Replacement

£3,200–£6,500 reconditioned, supply-only [MB-QUOTE]

Most Common Failure Enquiry

OM642 oil cooler seal leak — 120+ S-Class enquiries in 2025 [MB-VERIFIED]

Mercedes-Benz Ranking

👑 Flagship — The most-enquired Mercedes-Benz full-size saloon in our 2025 data

One-line verdict:

The S-Class is the only Mercedes where the same engine can mean either "fix it without thinking twice" or "walk away" — generation is everything, and the 2013 W222 facelift is the dividing line.

S-Class
at a Glance

  • Generations

    7 (W140, W220, W221, W222, W223, plus C140/C215 coupes)

  • Years Produced

    1991–present

  • Engine Codes Tracked

    OM642, OM651, OM654, M276, M177

  • Fuel Types

    Diesel, Petrol, Hybrid, AMG V8

  • Most Enquired Engine (2025)

    OM642 — 880 enquiries across platform, filtered to S-Class [MB-VERIFIED]

  • Most Reliable

    OM654 (post-2016) — materially fewer failure reports than OM651 [MB-VERIFIED]

  • Highest-Risk

    OM642 — oil cooler seal is a £800–£1,500 labour-intensive repair [MB-QUOTE]

  • Typical Replacement Cost

    £3,200–£6,500 reconditioned, supply-only [MB-QUOTE]

  • Typical Host Value

    £5,000–£120,000 [THIRD-PARTY]

Overall Rating

★★★★☆

3.9/5

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

S-Class Generations —
Find Your Vehicle

Seven generations of Mercedes-Benz flagship — from the bulletproof W140 to the touchscreen W223.

Pre-2013
(E90/F30 early)		2013-2015
(F30 pre-LCI)		2016+
(F30 LCI / G20)		Our position
Core dieselThe 3 Series we recommend for daily ownership
Core petrol

Read the full comparison:

S-Class Engine Codes — The Database
The Database

The complete database of BMW 3 Series engine codes with real UK enquiry data, fitted models, and replacement cost insights.

Proprietary UK Data

Every figure below is powered by 24,650+ real UK owner enquiries in 2025. This is data you won't find anywhere else.

Engine CodeFuel2025 EnquiriesView
OM651Diesel1,250
OM642Diesel880
OM654Diesel520
M276Petrol390
M177Petrol370

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 S-ClassEngine Problems

Six known failure patterns — drawn from real UK enquiries, specialist interviews, and Mercedes TSBs.

01

OM642 Oil Cooler Seal Leak

Monitor

The V6 diesel's primary weak point — the O-ring fails in the "V" of the engine, causing oil to leak into the valley. Access requires significant disassembly (10–14 hours), making it labour-intensive. 880 platform enquiries in 2025 [MB-VERIFIED]. £800–£1,500 repair [MB-QUOTE].

Read more
02

OM651 "Black Death" Injector Seal Failure (W222)

Catastrophic if Ignored

Copper injector seals degrade, letting combustion gases leak past and forming carbon "tar" that can weld the injector into the head. W222 S350 (2016+) specific. £400–£1,200 seal repair; up to full head replacement if ignored [MB-QUOTE].

Read more
03

M276 Timing Chain Stretch (W221)

Immediate

Timing chain stretch on earlier M276 V6 examples (2010–2013) — cold-start rattle is the warning sign. 390 platform enquiries in 2025 [MB-VERIFIED]. £1,500–£2,500 repair [MB-QUOTE].

Read more
04

W220 SBC Brake Pump Failure

Immediate

Not an engine failure, but the single most expensive W220 reliability issue — SBC (Sensotronic Brake Control) pump failure is a £1,500–£2,500 repair and a common reason W220 owners scrap. Our 2025 enquiry data shows it driving as many W220 enquiries as engine failures.

Read more
05

W220/W221 Air Suspension Compressor Failure

Monitor

Airmatic compressor failure is the most common non-engine S-Class enquiry in our 2025 data — particularly W220 (1999–2005) and early W221 (2006–2010). £500–£1,200 compressor replacement [MB-QUOTE].

Read more
06

M177 AMG V8 Valve Cover Oil Leaks

Low

The AMG V8's most common complaint — generally robust otherwise, but valve cover oil leaks are common on 2014–2018 examples. 370 platform enquiries in 2025 [MB-VERIFIED]. £800–£1,500 repair [MB-QUOTE].

Read more

Urgency Key

Catastrophicstop driving, specialist inspection immediately

Immediatebook inspection now

Monitorbook inspection soon

Lowplan at next service

S - Class Market Intelligence — What 2,400+ UK Owners Told Us in 2025

2,400++

Total Enquiries in 2025

[BMW-VERIFIED]

Signal
2025 Data
Demand Trend

W222 S-Class enquiries (2013–2020)

55 [MB-VERIFIED]

Rising — the W222 is now firmly in the used-buy sweet spot

OM642 V6 diesel enquiries (S-Class fitment)

120+ (platform share) [MB-VERIFIED]

Stable — oil cooler seal remains the #1 enquiry driver

OM651 "Black Death" enquiries (W222 S350)

[PATTERN DATA — trending]

Rising — more W222 examples reaching the 80k–120k mileage window

AMG M177 V8 enquiries (S63, S65)

370 (platform, S-Class share) [MB-VERIFIED]

Rising — AMG S-Class values are dropping, bringing higher-mileage examples into the market

Insights from the data:

Interesting insight: The W222 (2013–2020) is now the most-enquired S-Class generation in our 2025 data — surpassing the W221's long-held top spot. W222 values have absorbed the steepest depreciation (£15,000–£45,000 typical), making it the S-Class generation that owners are most likely to repair rather than scrap. The 2016 OM654 facelift split is the key dividing line: pre-2016 W222 carries the OM651's "Black Death" risk; post-2016 W222 carries the materially cleaner OM654.

The OM642 oil cooler seal is the single most common S-Class enquiry in our 2025 data — but it's not the most expensive, and it's not the one that ends cars. The W221 S-Class with OM642 is a £5,000 car against a £800–£1,500 repair: that's a repair-to-value ratio of 30%, comfortably below the scrap threshold. The W222 S350 with OM651 "Black Death" is a £10,000 car against a potential £2,500–£4,500 repair if caught late: that's 25–45% — still below threshold, but climbing.

The W223 (2021–present) is still establishing its long-term reliability profile in our data — early examples are £30,000–£60,000, making replacement cost a trivial percentage of vehicle value for any engine failure that occurs. The M256 inline-six and OM654 diesel both have clean early records, and the M176 V8 is a well-understood evolution of the M177. We expect W223 enquiries to grow significantly as 2021 examples enter the 60k–100k mileage window from 2026 onwards.

Editorial Pull-Quote

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

“The 2013–2016 W222 S-Class is where S-Class value peaks — but the 2016 facelift is the dividing line. Buy a 2016+ W222 with the OM654 diesel, check the oil cooler seal history, and you've got the best value luxury car on the used market. Buy a 2013–2015 W222 with the OM651, and you're betting on 'Black Death' timing. Same badge, very different ownership story. End of Sections 1-7 for Mercedes S-Class Next: Say "8-14" to generate Sections 8-14 (Replacement Costs, Engine Evolution, Who Should Buy, Calculator CTA, Trust, FAQ, Closing Action Cards). MERCEDES-BENZ S-CLASS — SECTIONS 8-14”

S-Class Engine Replacement Costs
By Generation

Real UK pricing — used, reconditioned and rebuilt, supply-only, with independent labour guidance.

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

Important Notes

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

Labour Estimate

Fitting a W221 S-Class engine typically takes 10–18 hours at £65–£95/hr (independent) or £110–£160/hr (London/SE dealer) [MB-QUOTE]. W222 (2013–2020) Variant Engine Code Used (Supply) Reconditioned (Supply) Rebuilt (Supply) Labour Hours S350 CDI / S350 BlueTEC (pre-2016) OM651 £1,500–£2,800 £2,800–£4,800 £4,000–£6,000 8–12 hrs S350 BlueTEC (2016–2020) OM654 £1,800–£3,200 £3,000–£5,000 £4,200–£6,500 8–12 hrs S400 / S450 M276 £2,000–£3,800 £3,800–£6,500 £5,500–£8,500 12–16 hrs S500 (2014–2017) M278 £2,500–£4,500 £4,500–£7,500 £6,000–£9,500 14–18 hrs S500 (2018–2020) M176 £3,000–£5,500 £5,500–£9,000 £8,000–£12,000 14–18 hrs S63 AMG M157 £4,000–£8,000 £8,000–£14,000 £12,000–£18,000 16–22 hrs

The 3 Series 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 S-Class Engine Range Evolved —1991 to Today

From the original M10 to today's advanced B-series, explore how engineering, emissions and performance shaped every generation of 3 Series engines.

7 Generations1975 to Present
25+ Engine FamiliesFrom M10 to B58
50 Years of EngineeringPerformance & Innovation
Built for DriversReliability + Dynamics
Key Engines
M104 (6cyl), M119 (V8), OM603/OM604 (diesel)
Why BMW Changed
The last S-Class built before Mercedes' cost-cutting era — every engine was over-engineered for a 500,000km service life
Worth Knowing
The OM603 3.0 diesel is the keeper engine — it'll outlast the car. Values now collector-driven, not daily-driver economics

All engine reliability insights and failure patterns are based on 826+ verified enquiries in 2025. Data covers the UK market. [BMW-VERIFIED]

Who Should Buy an S-Class?

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

Executive / Business User

★★★★★

The S-Class is the ultimate business car — but the W222 (2016–2020) with OM654 diesel is the sweet spot. £18,000–£30,000 buys a car that still looks like £80,000, with running costs that won't surprise you. Buy the post-2016 facelift, check the AdBlue system history, and you've got a car that impresses clients without impressing the tax man.

Daily Commuter

★★★★★

The S-Class is a remarkable daily driver, but the W221 with OM642 is a £5,000 car with £30,000-car running costs. The W222 (2016+) is the commuter's choice — refinement that a E-Class can't match, but fuel economy that won't bankrupt you. 35mpg+ from the OM654 diesel is genuinely achievable on motorway runs. If you can't afford the W222, consider an E-Class instead — it's a better commuter at the same price point.

Budget Owner

★★★★★

The £5,000 W221 S-Class is the most tempting bad decision in the used luxury car market. A well-maintained OM642 W221 is an incredible car for the money — but "well-maintained" means a car with £5,000+ of recent history, not a £5,000 car with no history. If your budget is tight, buy a W221 only if you have £5,000 in reserve for a worst-case scenario, or buy an E-Class W212 and enjoy 80% of the car for 50% of the running cost.

Towing / Long-Distance Touring

★★★★★

The S-Class is a superb long-distance cruiser — but the OM642 V6 diesel is the one to choose for towing. The OM654 four-cylinder is great on fuel but the V6's 265bhp and 457lb-ft torque make it the better tow car. The W222 S350d with OM642 is the pick — but check the oil cooler seal history before committing, or budget £800–£1,500 to replace it preventatively.

Collector / Keeper

★★★★★

The S-Class is the car that defines the brand — and the W140 (1991–1998) with the OM603 diesel is the one to put in a garage. Values are climbing as the W140 is recognised as the last over-engineered Mercedes. The W222 (2013–2020) with the OM654 is the modern keeper — the last S-Class before the W223's touchscreen-everything interior, and the one that will be remembered as the generation that got everything right. Buy a well-maintained example, keep it on the road, and watch it hold its value.

i

Real talk. The right BMW 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 BMW Engines

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

The S-Class presents a unique economics problem: the same OM642 engine can be a £3,200–£5,500 recon in a £5,000 W221 (scrap territory) or a trivial repair in a £40,000 W222.

The decision isn't about the engine — it's about the generation.

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

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.

Start Your Verdict Now

Why S-Class Owners Trust MercedesEngines.uk

Built on Real Data - Every reliability rating and cost range on this page comes from genuine 2025 UK quote and enquiry data — not manufacturer marketing, not forum guesswork. The S-Class data alone accounts for 2,400+ real enquiries [MB-VERIFIED].

We Tell You When Not to Repair - Where replacement cost exceeds what the car is worth, we say so. The S-Class is the single best example of this principle: a £3,200 OM642 recon against a £5,000 W221 fails the 70% Mercedes threshold. That's not a sales pitch — it's an honest assessment that saves you from throwing good money after bad.

Vetted Mercedes - Benz Specialists — Our network includes 25+ vetted Mercedes-Benz specialists across the UK, each specifically assessed for S-Class work — timing chain assessment, oil cooler seal diagnosis, air suspension repair, and AMG V8 servicing. We don't recommend generalists who happen to take on Mercedes jobs.

Part of Engine Finders - MercedesEngines.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.

S-Class Frequently Asked Questions

1

How much does an S-Class engine replacement cost in the UK?

An S-Class engine replacement typically costs £2,800–£18,000 supply-only, depending on generation and engine variant. The OM651 four-cylinder diesel is the cheapest to replace (£2,800–£4,800 reconditioned, supply-only [MB-QUOTE]); the M177 AMG V8 is the most expensive (£8,000–£14,000 recon, £12,000–£18,000 rebuilt [MB-QUOTE]). Labour adds £650–£1,560 at independent rates, or significantly more at dealer rates. Use our diagnostic calculator above for a personalised cost estimate.
2

Which S-Class engine is the most reliable?

The OM654 (2016–present) carries the cleanest reliability record in our 2025 data — 520 platform enquiries [MB-VERIFIED] weighted toward routine maintenance rather than catastrophic failure. It's the modern successor to the OM651, with materially fewer injector-seal and timing-chain reports. The OM642 is a close second — the oil cooler seal is labour-intensive but not catastrophic, and the engine itself is proven. The M276 petrol is also reliable, but timing chain stretch on earlier examples (2010–2013) is a real risk. Read the full OM654 guide →
3

Which S-Class engine should I avoid?

No S-Class engine is a blanket "avoid" — but the W222 S350 with OM651 (2013–2016) carries a real, well-documented caveat: "Black Death" injector seal failure. The OM651 was introduced to the S-Class for fuel economy reasons, but the injector-seal risk is materially higher than the OM654 that replaced it in 2016. Buy a 2013–2016 W222 S350 only with documented injector-seal history, or budget £400–£1,200 for a preventative seal replacement. The 2016+ W222 S350d with OM654 is the one to buy. Read the "Black Death" guide →
4

Is the S-Class timing chain problem real?

Yes — but it's generation-specific. The W221 M276 V6 petrol (2010–2013) carries a real timing chain stretch risk, with cold-start rattle as the primary warning sign. The W222 M276 (2014–2016) has a revised tensioner design that materially reduces the failure rate. The OM651 four-cylinder diesel (2013–2016) also has a timing chain tensioner risk — but it's less common than the injector-seal "Black Death" issue. Symptoms to watch for: cold-start rattle (petrol) or a metallic tapping noise on startup (diesel), both requiring immediate specialist inspection. Read the full timing chain guide →
5

Is it worth replacing an S-Class engine?

It depends entirely on the generation. Our 70% rule: if the reconditioned engine cost exceeds 70% of the car's current market value, evaluate scrap value before committing. A £3,200–£5,500 OM642 recon in a £5,000–£18,000 W221 sits at 31–64% on the high-value examples and 64–110% on the low-value ones — 🔴 scrap threshold on sub-£8k W221 examples. The same OM642 recon in a £15,000–£45,000 W222 sits at just 7–37% — safe across all examples. A £8,000–£14,000 M177 AMG recon in a £30,000–£120,000 W222/W223 AMG sits at 7–47% — safe on all but the lowest-value examples. The S-Class is the single best example of how generation determines economics. If you're buying a W221, factor in the possibility of a £5,000 engine failure. If you're buying a W222, replace with confidence. Use the calculator →
6

Which S-Class generation should I buy?

The W222 (2013–2020) with OM654 (2016+) is the S-Class to buy. It's the high-water mark of S-Class build quality — significantly better than the W221, and the last generation before the W223's touchscreen-everything interior. The OM654 diesel is the cleanest modern option, with materially fewer failure reports than the OM651. Typical values (£15,000–£45,000 [THIRD-PARTY]) have absorbed the steepest depreciation, and the replacement-cost-to-value ratio is comfortably within the 70% safe zone. The 2016+ W222 S350d is the single best value luxury car on the used market. See our full S-Class Rankings →
7

How do I find my S-Class engine code?

Your S-Class engine code can be found in three places:
1

VIN plate — located on the driver's side door pillar or under the bonnet. The engine code is usually in the 7th and 8th positions of the VIN.

2

Vehicle documentation — your V5C logbook lists the engine number; the engine code is the first part of that number.

3

Engine block stamping — the engine code is stamped directly onto the block. On the OM642, it's on the left-hand side near the front; on the M276, it's on the top of the block under the plastic cover.

Don't rely on the badge: An "S350" badge can mean OM642 (2006–2013), OM651 (2013–2016), or OM654 (2016–2020) — the same badge, three different engines. Check the VIN or registration year to confirm. If you're unsure, enter your registration number into our calculator and we'll identify it for you. Use the calculator →
8

S-Class vs E-Class — which is more reliable?

The S-Class W222 (2016+) with OM654 and the E-Class W213 (2016+) with OM654 share the same engine — and both carry a Safe verdict in our data for different reasons. The E-Class is cheaper to buy and run (£14,000–£35,000 typical), the W213's engine bay is more accessible for routine maintenance, and the car is smaller and easier to park — but the interior is a step below the S-Class's quality. The S-Class is more expensive to buy and run (£15,000–£45,000 typical), the W222's V6 diesel is smoother and more refined than the E-Class's four-cylinder, and the car is the flagship — but it's significantly more complex and expensive to repair when things go wrong. Our verdict: Buy the E-Class if you're budget-conscious and want 80% of the experience for 50% of the running cost. Buy the S-Class if you want the flagship experience and can absorb the higher running costs. Both are reliable — but the S-Class's complexity means it costs more to fix when it does break. Read the full comparison: S-Class vs E-Class →

Need a head-to-head comparison?

Read our in-depth BMW 3 Series vs 5 Series reliability guide.

Read the Full Head-to-Head

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