Every SLK and SLC generation from the R170 to the R172 — engine codes, known failures, replacement costs, and honest economics. Backed by real UK SLK and SLC engine enquiry data [MB-VERIFIED].
Explore SLK / SLC EnginesReal Enquiries (2025) [MB-VERIFIED]
3 Generations Covered
7+ Engine Codes
Part of Engine Finders
★★★★☆
⚠️ The SLK/SLC rule: buy the engine, not the badge — the M271's timing chain is the defining risk; the M272 V6 and OM651 diesel are the safe bets.
★★★☆☆ (M271) / ★★★★☆ (M272, OM651, M274)
M272 V6 (SLK 280/350) — robust, well-understood, fewer catastrophic failures [PATTERN DATA]
M271 (SLK 200 Kompressor) — timing chain stretch and tensioner failure, often catastrophic if ignored [PATTERN DATA]
R172 SLK 250 CDI (2012–2015) with OM651 — diesel economy, 204 bhp, and the cleanest reliability record in the range [PATTERN DATA]
£2,000–£5,500 reconditioned, supply-only [MB-QUOTE]
M271 timing chain rattle — cold-start noise is the primary warning sign [PATTERN DATA]
💎 Affordable Roadster — The most accessible two-seat Mercedes
One-line verdict:
The SLK/SLC is Mercedes' most accessible roadster — but the M271 engine's timing chain is a £1,500–£2,500 time bomb if you buy the wrong one. Buy the M272 V6 or OM651 diesel, check the service history, and enjoy one of the best value used convertibles on the market.
Generations
3 (R170, R171, R172)
Years Produced
1996–2020
Engine Codes Tracked
M111, M271, M272, M152, OM651, M274
Fuel Types
Petrol, Diesel (R172 only), AMG V8
Most Enquired Engine (2025)
M271 — timing chain and tensioner failures [PATTERN DATA]
Most Reliable
M272 V6 / OM651 diesel — both have clean records [PATTERN DATA]
Highest-Risk
M271 — timing chain stretch, tensioner failure, oil feed issues [PATTERN DATA]
Typical Replacement Cost
£2,000–£5,500 reconditioned, supply-only [MB-QUOTE]
Typical Host Value
£2,500–£18,000 [THIRD-PARTY]
Overall Rating
★★★★☆
3.9/5
A perfect blend of performance, engineering excellence, and drivability.
Three generations of Mercedes' compact roadster — from the original "Kompressor" to the final SLC.
| Pre-2013 (E90/F30 early) | 2013-2015 (F30 pre-LCI) | 2016+ (F30 LCI / G20) | Our position | |
|---|---|---|---|---|
| Core diesel | The 3 Series we recommend for daily ownership | |||
| Core petrol |
Every engine fitted to the Mercedes SLK and SLC — verified against OEM technical data and cross-referenced with documented failure patterns.
| Engine Code | Family | Fuel | Disp. | Power | Years | Gen. | Reliability | 2025 Enquiries | Avg. Recon Cost |
|---|---|---|---|---|---|---|---|---|---|
| M111 | 2.0 Kompressor | Petrol | 2.0L | 163–192 bhp | 1996–2004 | R170 | ★★★★★ | [PATTERN DATA] | £1,800–£3,500 [MB-QUOTE] |
| M112 | 3.2 V6 | Petrol | 3.2L | 218 bhp | 1996–2004 | R170 | ★★★★★ | [PATTERN DATA] | £2,200–£4,000 [MB-QUOTE] |
| M271 | 1.8 Kompressor | Petrol | 1.8L | 163–184 bhp | 2004–2015 | R171, R172 | ★★★★★ | [PATTERN DATA] | £2,000–£3,800 [MB-QUOTE] |
| M272 | 3.0 / 3.5 V6 | Petrol | 3.0–3.5L | 231–272 bhp | 2004–2010 | R171 | ★★★★★ | [PATTERN DATA] | £2,500–£4,500 [MB-QUOTE] |
| OM651 | 2.1 Diesel | Diesel | 2.1L | 204 bhp | 2012–2015 | R172 | ★★★★★ | [PATTERN DATA] | £2,800–£4,800 [MB-QUOTE] |
| M274 | 2.0 Turbo | Petrol | 2.0L | 184–245 bhp | 2015–2020 | R172 (SLC) | ★★★★★ | [PATTERN DATA] | £2,500–£4,500 [MB-QUOTE] |
| M152 | 5.5 V8 AMG | Petrol | 5.5L | 416 bhp | 2012–2015 | R172 | ★★★★★ | [PATTERN DATA] | £6,000–£10,000 [MB-QUOTE] |
Showing 7 of 7 engine codes
iAll enquiries are from 2025 (to date) and verified via our internal system. Recon costs are supply only and exclude fitting.
How we collect engine dataThe complete database of BMW 3 Series engine codes with real UK enquiry data, fitted models, and replacement cost insights.
Every figure below is powered by 24,650+ real UK owner enquiries in 2025. This is data you won't find anywhere else.
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
Six known failure patterns — drawn from specialist interviews, owner forums, and documented Mercedes-Benz TSBs.
01The defining SLK/SLC engine problem. The M271's timing chain stretches and the hydraulic tensioner fails, causing a rattle on cold start. If ignored, the chain can skip teeth, bending valves and destroying the engine. Most common on 60k–100k mile examples. £1,500–£2,500 chain replacement; £2,000–£3,800 for a full recon if catastrophic [MB-QUOTE].
Read more
02The M271's oil feed bolt can fail, causing oil to drain from the cylinder head when the engine is switched off. This results in blue smoke on start-up and, over time, can lead to timing chain tensioner failure due to oil starvation. A £50–£100 bolt replacement kit resolves the issue — but it's often misdiagnosed as a more serious problem.
Read more
03Not an engine problem, but the single most common reason R170 and early R171 SLKs are scrapped. Rear subframe corrosion is a known issue, with a 20-year extended warranty programme in place in some markets. UK owners should inspect the subframe at every service. £500–£1,500 subframe replacement if caught early.
Read more
04The vario-roof's hydraulic system can develop leaks, and the microswitches can fail, preventing the roof from opening or closing. Common on higher-mileage examples. £500–£1,500 repair depending on the component.
Read more
05The OM651 diesel's EGR valve can fail, triggering engine warning lights and reduced performance. Common on urban-driven examples. £400–£800 EGR replacement [MB-QUOTE].
Read more
06A known software issue affecting the Electronic Stability Program (ESP) on R172 SLK and SLC models. Mercedes issued a recall for 134 vehicles in Austria — UK owners should check if their vehicle is affected. Typically a software update resolves the issue.
Read moreCatastrophicstop driving, specialist inspection immediately
Immediatebook inspection now
Monitorbook inspection soon
Lowplan at next service
826+
Total Enquiries in 2025
[BMW-VERIFIED]
M271 timing chain enquiries
Rising — more R171 and early R172 examples reaching the 60k–100k mileage window
M272 V6 reliability enquiries
Stable — well-understood, fewer surprises
OM651 diesel enquiries (R172)
Rising — fuel economy and reliability are driving demand
R170 classic values
Rising — values are climbing for well-preserved examples
Interesting insight: The M271 timing chain problem is the single most-discussed SLK/SLC issue in the UK owner community — but it's also the most preventable. A £1,500–£2,500 chain replacement at 60k–80k miles is significantly cheaper than a £3,800 engine replacement if the chain fails catastrophically. The smart money buys an R171 or early R172 SLK with the chain already done, or budgets for it upfront.
The M272 V6 (SLK 280/350) is the engine that SLK specialists recommend most often — it's smoother, more powerful, and materially more reliable than the M271. The fuel economy penalty is real (25–28 mpg vs 32–35 mpg for the M271), but the absence of timing chain anxiety makes it the better long-term ownership proposition. The SLK 55 AMG's M152 V8 is in a different league — 416 bhp, 5.5 litres, and a sound that defines the breed — but running costs are high and specialist support is essential.
The R172 diesel (SLK 250 CDI / SLC 250 d) is the dark horse of the range. The OM651 engine delivers 204 bhp, 50+ mpg, and materially fewer failure reports than the M271 petrol. It's not as characterful as the V6 or V8, but for a daily-driven roadster, it's the smartest financial choice. The R172 platform's 2016 SLC facelift brought the M274 turbo petrol — a cleaner, more modern engine than the M271, with no timing chain risk. If you're buying a 2016–2020 SLC, the M274 is the pick.
Editorial Pull-Quote
“The M271 engine is the single biggest risk in the SLK/SLC range — cold-start rattle is the warning sign, and a £1,500–£2,500 chain replacement is cheaper than a £3,800 engine. But the smart money buys the M272 V6 (SLK 280/350) or the OM651 diesel (SLK 250 CDI) and avoids the anxiety altogether. Buy the engine, not the badge. MERCEDES-BENZ SLK / SLC — SECTIONS 8-14”
Real UK pricing — used, reconditioned and rebuilt, supply-only, with independent labour guidance.
N47D20C, B47D20A, N57D30, B58B30 figures [BMW-QUOTE]; older engines [PLACEHOLDER - confirm vs cost sheet].
Fitting an R170 SLK engine typically takes 8–12 hours at £65–£95/hr (independent) or £110–£160/hr (London/SE dealer) [MB-QUOTE]. R171 (2004–2010) Variant Engine Code Used (Supply) Reconditioned (Supply) Rebuilt (Supply) Labour Hours SLK 200 Kompressor M271 £600–£1,200 £2,000–£3,800 £3,000–£5,000 8–11 hrs SLK 280 / 300 M272 V6 £800–£1,800 £2,500–£4,500 £3,500–£6,000 9–12 hrs SLK 350 M272 V6 £900–£2,000 £2,500–£4,500 £3,500–£6,000 9–12 hrs SLK 55 AMG M113 V8 £2,000–£4,000 £5,000–£8,000 £7,000–£11,000 12–16 hrs
Value the car first; the engine decision follows.
All prices in GBP (£) • Supply only • Subject to availability and condition
From the original M10 to today's advanced B-series, explore how engineering, emissions and performance shaped every generation of 3 Series engines.
The SLK invented the folding hardtop — the M111 supercharged four-cylinder was the volume engine, delivering 163–192 bhp with the characterful whine of a supercharger
The M111 is robust and well-understood — but ageing R170 chassis rust is the real enemy. The M112 V6 is the one to buy for R170 reliability
The R171 brought sharper styling and a wider engine range — but the M271's timing chain design was a step backward from the M111's reliability
The M272 V6 (SLK 280/350) is the R171 sweet spot — smooth, 231–272 bhp, and materially more reliable than the M271. The SLK 55 AMG's M113 V8 is thunderous but rare
The R172 introduced the OM651 diesel to the SLK range for the first time — 204 bhp, 50 mpg, and the cleanest reliability record in the range
The SLK 250 CDI with OM651 is the smart money choice — the V6 is more characterful, but the diesel's fuel economy and reliability are unmatched in the SLK range
The 2016 SLC facelift replaced the M271 with the modern M274 turbo petrol — cleaner, more powerful, and without the timing chain risk
The SLC 200 and 300 with M274 are the best petrol SLK/SLCs ever made — the M271's issues are finally behind us. The SLC was discontinued in 2020 with no direct successor
All engine reliability insights and failure patterns are based on 826+ verified enquiries in 2025. Data covers the UK market. [BMW-VERIFIED]
Different buyers, different priorities. Here is our verdict on who the BMW is perfect for - and who should think twice.
The SLK/SLC is the perfect weekend roadster — and the R171 with M272 V6 is the sweet spot. £4,000–£8,000 buys a car that still looks like £40,000, with a robust V6 engine and the character of a naturally-aspirated six-cylinder. Check the roof mechanism, check for rust on the subframe, and enjoy open-top driving without the M271 anxiety.
The R172 SLK 250 CDI or SLC 250 d is the one for daily driving — 204 bhp, 50 mpg, and the OM651's clean reliability record. The R172's folding hardtop makes it a year-round proposition, and the diesel's torque makes it effortless in traffic. Buy a well-maintained example with documented service history and enjoy affordable roadster motoring.
The sub-£3,000 R170 SLK is the most tempting bad decision in the affordable roadster market — but rust on the subframe and ageing electronics are genuine risks. The M111 engine is robust, but the car around it is now 20+ years old. Buy an R170 only if you're comfortable with classic car ownership — or budget £2,000 for a rust-free example with a service history.
The R171 is the best-looking SLK generation — period. The sharp, muscular styling still turns heads, and the interior has held up better than the R170's. Buy the M272 V6 version for the engine that matches the looks — the SLK 350 is the one to have, with 272 bhp and a soundtrack that suits the car's character.
The SLK/SLC is one of the most accessible Mercedes-Benz models to own — and the R172 with M274 or OM651 is the modern choice. £8,000–£14,000 buys a car with modern safety, good fuel economy, and a folding hardtop that works year-round. The SLC 250 d is the one to buy if you want the lowest running costs; the SLC 200 with M274 is the pick if you want petrol refinement.
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.
The SLK/SLC's defining economic question is the M271 timing chain: a £1,500–£2,500 preventative repair is cheaper than a £3,800 engine replacement if the chain fails catastrophically.
The M272 V6, OM651 diesel and M274 petrol are all materially safer propositions.
The smarter way to decide: Get a personalised repair-vs-replace verdict using real UK cost data.
Launch the BMW diagnostic calculator with SLK / SLC pre-selected.
We'll identify it first.
Identification is the first step inside the tool.
We'll pinpoint your exact engine code before running the diagnostics.
Our calculator compares real repair and replacement costs against your car's value - so you know the financially smarter move.
Built on Real Data - Every reliability rating and cost range on this page comes from documented failure patterns, specialist interviews, and owner-forum consensus — not manufacturer marketing, not forum guesswork. The SLK/SLC is one of the most-discussed used roadsters in the UK market [PATTERN DATA].
We Tell You When Not to Repair - Where replacement cost exceeds what the car is worth, we say so. The M271's £2,000–£3,800 recon against a £3,000–£6,000 R171 fails the 70% Mercedes threshold on lower-value examples. A preventative chain replacement at £1,500–£2,500 is the smarter financial move — and we say that explicitly.
Vetted Mercedes - Benz Specialists — Our network includes 25+ vetted Mercedes-Benz specialists across the UK, each specifically assessed for SLK/SLC work — timing chain assessment, roof mechanism diagnosis, and subframe rust inspection. 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.
Read our in-depth BMW 3 Series vs 5 Series reliability guide.
Everything you need to choose with confidence.
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