Every B-Class generation covered — W245 and W246, petrol and diesel, real UK running costs and reliability data from 177+ real enquiries in 2025 [MB‑VERIFIED]. Backed by the UK's most trusted Mercedes-Benz specialist network.
Explore B-Class Engines177+ Enquiries (2025) [MB‑VERIFIED]
2 Generations Covered
5 Engine Codes
Part of Engine Finders
★★★★☆
✅ The B-Class rule: generation is everything — the W246 (2011–2018) comfortably justifies replacement; the W245 (2005–2011) frequently doesn't
★★★★☆
OM651 2.1 CDI — the modern diesel that powers the W246; far fewer failure reports than the earlier OM640 [MB‑VERIFIED]
OM640 2.0 CDI — early W245 diesel with injector and EGR issues; pre-2008 examples particularly affected [PATTERN DATA]
W246 B200 CDI (2014–2018) — post-facelift OM651, 158‑enquiry sweet spot with £2,800–£4,800 recon cost against £5,000–£14,000 vehicle value [MB‑VERIFIED]
£2,800–£4,800 (recon, supply-only) [MB‑QUOTE]
OM651 injector seal / "Black Death" — 80%+ of B-Class diesel enquiries [MB‑VERIFIED]
🥇 Best Family MPV — the safest, most family-friendly Mercedes in the compact segment
One-line verdict:
The B-Class is the Mercedes family MPV that genuinely makes sense — buy a post-2014 W246 with the OM651 diesel, give the early W245 petrols a miss, and you'll have a safe, affordable, long-lasting car that won't punish you at repair time.
Generations
2 (W245, W246)
Years Produced
2005–present (2018–present: W247, omitted from core data)
Engine Codes Tracked
5
Fuel Types
Diesel, Petrol
Most Enquired Engine (2025)
OM651 2.1 CDI — 157 enquiries (W246) [MB‑VERIFIED]
Most Reliable
OM651 2.1 CDI (post-2014)
Highest-Risk
OM640 2.0 CDI (pre-2008)
Typical Replacement Cost
£2,800–£4,800 (recon) [MB‑QUOTE]
Typical Host Value
£5,000–£14,000 (W246) / £1,500–£5,000 (W245) [THIRD‑PARTY]
Overall Rating
★★★★☆
3.9/5
A perfect blend of performance, engineering excellence, and drivability.
The B-Class runs in two distinct generations — the earlier W245 (2005–2011) and the more modern W246 (2011–2018). The dividing line is sharp.
| 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 B-Class engine code ever offered in the UK — verified against factory technical specs and cross‑referenced with real 2025 enquiry data.
| Engine Code | Family | Fuel | Disp. | Power | Years | Gen. | Reliability | 2025 Enquiries | Avg. Recon Cost |
|---|---|---|---|---|---|---|---|---|---|
| OM640 | 2.0 CDI | Diesel | 2.0L | 109–140 bhp | 2005–2011 | W245 | ★★★★★ | [PATTERN DATA] | £2,800–£4,800 [MB-QUOTE] |
| OM651 | 2.1 CDI | Diesel | 2.1L | 136–177 bhp | 2011–2018 | W246 | ★★★★★ | 157 [MB-VERIFIED] | £2,800–£4,800 [MB-QUOTE] |
| M266 | 1.5/2.0 petrol | Petrol | 1.5–2.0L | 95–136 bhp | 2005–2011 | W245 | ★★★★★ | [PATTERN DATA] | £1,800–£3,200 [MB-QUOTE] |
| M270 | 1.6/2.0 turbo petrol | Petrol | 1.6–2.0L | 122–211 bhp | 2011–2018 | W246 | ★★★★★ | [PATTERN DATA] | £1,800–£3,500 [MB-QUOTE] |
| M274 | 2.0 turbo petrol | Petrol | 2.0L | 184–211 bhp | 2015–2018 | W246 | ★★★★★ | [PATTERN DATA] | £2,000–£3,800 [MB-QUOTE] |
Showing 5 of 5 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
The failures B-Class owners actually encounter — ranked by severity and backed by 177+ real UK enquiries.
01The defining diesel issue across all OM651‑powered Mercedes models — copper injector seals degrade, allowing combustion gases to leak past and form a thick carbon "tar" around the injector base. Left untreated, the carbon can weld the injector into the cylinder head, turning a £400–£1,200 seal job into a full cylinder‑head repair or engine replacement. Most common on B‑Class W246 examples from 2012–2016 with 70,000–100,000 miles. [MB‑VERIFIED]
Read more
02The earlier W245 diesel — injector leak‑off issues and EGR valve clogging are both common. The OM640's EU4 emissions hardware was more sensitive than the later OM651; repair costs typically £300–£800 per injector, £400–£1,200 for EGR replacement. Pre‑2008 units particularly affected [PATTERN DATA].
Read more
03On the 1.6‑litre and 2.0‑litre turbo petrol variants, the turbocharger's oil supply line can become restricted (sludge buildup from extended service intervals). Warning signs: high‑pitched whine under acceleration, oil consumption above 1L/1,000 miles. Typically occurs 60,000–100,000 miles [PATTERN DATA].
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04The 1.5‑litre and 2.0‑litre naturally‑aspirated petrols in the W245 — timing chain tensioner wear can lead to chain rattle on cold start. Unlike the OM651's rear‑chain complexity, the M266's chain is front‑mounted, making inspection and replacement relatively straightforward. Still, if ignored, the chain can skip and the engine will need a rebuild [PATTERN DATA].
Read more
05Post‑2014 W246 B‑Class with OM651 diesel — AdBlue system warnings are the most common non‑engine failure in our W246 B‑Class data. Typically NOx sensor or heater failure, software‑manageable, £400–£1,200 repair. Not a showstopper, but frustrating and needs addressing [MB‑VERIFIED].
Read more
06Both OM640 and OM651 diesels — DPF regen cycles fail to complete on short, cold urban trips. The B‑Class is often bought as a city MPV, which directly exacerbates this problem. Symptoms: limp mode, fuel‑diluted oil, £400–£1,200 for DPF clean or replacement. The fix is a 30‑minute motorway run at 2,500rpm once a month — but many owners don't know that [MB‑VERIFIED].
Read moreCatastrophicstop driving, specialist inspection immediately
Immediatebook inspection now
Monitorbook inspection soon
Lowplan at next service
177++
Total Enquiries in 2025
[BMW-VERIFIED]
W246 B‑Class Enquiries
Rising[PLACEHOLDER — YoY % from source data]
W245 B‑Class Enquiries
Stable[PLACEHOLDER — YoY % from source data]
OM651‑vs‑OM640 Split
Stable
Interesting insight: The B‑Class's 177 total enquiries make it one of the quieter Mercedes models in our 2025 dataset — but the 88% / 12% split between W246 and W245 is the sharpest generational divide in the entire Mercedes line‑up. Buyers are actively avoiding the first‑generation W245; the second‑generation W246 accounts for almost nine out of ten enquiries.
The OM651's "Black Death" injector‑seal failure is the single biggest driver of B‑Class diesel enquiries — but because it's a cheap, preventable fix if caught early, the OM651 is still the recommended engine. The W245's OM640 doesn't have the same known‑issue‑with‑known‑fix profile; its failures are more varied and less predictably repairable.
The B‑Class is the only Mercedes MPV that carries a ✅ Safe verdict without major caveat in our data — the V‑Class and Viano are larger and more expensive to run; the B‑Class is the genuinely family‑friendly option.
Editorial Pull-Quote
“Buy a W246 B‑Class from 2014 onwards with the OM651 diesel, and ignore the service‑history‑scare stories — the "Black Death" injector seal is a cheap, manageable fix if caught early. The W245 isn't necessarily a bad car, but at current market values, a new engine will cost more than the car is worth. The generation‑based advice on the B‑Class is as clear as it gets. MERCEDES B-CLASS — SECTIONS 8-14”
Real UK pricing for every B-Class engine — used, reconditioned and rebuilt options, supply-only, with independent labour guidance. All figures [MB-QUOTE].
| Variant | Engine Code | Used (Supply) | Reconditioned (Supply) | Rebuilt (Supply) | Labour Hours |
|---|---|---|---|---|---|
| B180 CDI / B200 CDI | OM640 | £500–£1,200 | £2,800–£4,800 | £4,000–£6,000 | 8–10 hrs |
| B150 / B170 / B200 | M266 1.5/2.0 petrol | £400–£900 | £1,800–£3,200 | £2,800–£4,500 | 7–9 hrs |
N47D20C, B47D20A, N57D30, B58B30 figures [BMW-QUOTE]; older engines [PLACEHOLDER - confirm vs cost sheet].
Fitting a B-Class engine typically takes 7–10 hours at £65–£95/hr (independent) or £110–£160/hr (London/SE dealer) [MB-QUOTE]. The B-Class rule — generation is everything: A W245 B200 CDI (OM640) at typical market value of £1,500–£5,000 against a £2,800–£4,800 recon cost sits at 56–96% — at or above our 70% threshold for many examples [THIRD-PARTY]. The honest advice: unless the car has sentimental value or a documented recent engine, walk away from a W245 diesel with a failed engine. A W246 B200 CDI (OM651) at £5,000–£14,000 against the same £2,800–£4,800 recon cost sits at 20–56% — comfortably below the threshold in most cases [MB-QUOTE]. Fix the W246; scrap the W245 (unless it's a low‑mileage, well‑kept petrol example).
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.
Mercedes entered the compact MPV segment with the B-Class — the first car to use the "sandwich floor" chassis (engine and transmission partially under the cabin).
The OM640 diesel is an older EU4 design — injector and EGR failures are common on higher‑mileage examples. The M266 petrols are simpler and more reliable but less economical.
Mercedes updated the B-Class to use the MFA platform (same as A‑Class) — a far more modern architecture that allowed turbocharging across the range and full EU5 compliance.
This is the defining era. The OM651 is the defining diesel of a generation — 157 enquiries in 2025 [MB‑VERIFIED], and the "Black Death" injector seal failure is the only major caveat.
Facelift electronics, emissions hardware (AdBlue on post‑2014 diesels), and a more refined cabin. The M274 replaced the M270 2.0‑litre petrol as a higher‑output option.
Post‑2014 W246 B‑Class with OM651 is the sweet spot — AdBlue system issues are the main (and low‑severity) caveat. The B‑Class is the ✅ Safe family MPV.
Emissions‑driven: the OM654 replaced the OM651 across the Mercedes range, and the M282 1.3‑litre petrol is Renault‑sourced (a platform‑sharing decision with the A‑Class).
The W247 B‑Class is outside our core 2025 data — but it's a less‑common UK choice, with the A‑Class taking most of the compact‑Mercedes market.
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 B-Class is perfect for - and who should think twice.
The B‑Class is the most family‑friendly compact Mercedes in our data — the W246 has the same OM651 engine as the C‑Class but with higher‑roof practicality and lower purchase prices. Buy a 2014–2018 B200 CDI, ignore the "MPV" stigma, and enjoy a safe, reliable family car that doesn't cost a fortune to run.
The OM651 diesel is the motorway‑mile champion — 45–55 mpg, comfortable ride, and enough power for A‑road overtakes. The B‑Class is less common than the A‑Class as a commuter car, but that means lower prices and less competition in the used market.
This is where the generation split matters. A W245 B‑Class (2005–2011) can be bought for £1,500–£3,000, but a £2,800–£4,800 recon engine is an existential threat to the car's value — you're one failure away from scrapping it. A W246 (2011–2018) at £5,000–£8,000 is a safer budget bet — recon cost sits at 35–60% of vehicle value, which is manageable [MB‑QUOTE].
If you need a Mercedes badge but don't want the running costs of an E‑Class or the complexity of a GLC, the B‑Class is the sensible choice. It's the only Mercedes MPV with a ✅ Safe verdict across most examples — the V‑Class is expensive to run and the Viano is discontinued. The B‑Class is the budget‑friendly practical Mercedes.
The B‑Class is often someone's first Mercedes — the W246 offers the brand's quality, safety and diesel‑reliability at a price that doesn't intimidate. Buy the 2014+ OM651, budget £400–£800 for a preventative injector‑seal check, and you'll have a car that's genuinely cheaper to run than many non‑premium alternatives [EM‑INTERVIEW].
Real talk. The right B-Class 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 B‑Class's economics are sharply divided by generation — a W246 is almost always worth fixing; a W245 diesel often isn't.
If your W246 B‑Class has an injector‑seal failure (the most common B‑Class diesel problem in our data), a £400–£1,200 repair is a no‑brainer [MB‑VERIFIED]. But if the engine has suffered terminal bottom‑end damage (rare on the OM651), the repair‑vs‑replace decision is about to get harder — use our calculator to get a personalised verdict.
The smarter way to decide: Get a personalised repair-vs-replace verdict using real UK cost data.
Launch the BMW diagnostic calculator with B-Class 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 figure on this page is drawn from 177+ real UK B‑Class enquiries in 2025 [MB‑VERIFIED] — not manufacturer marketing, not forum guesswork.
We Tell You When Not to Repair - When a W245 B‑Class diesel's replacement cost exceeds 70% of the car's value, we say so. That's the difference between a knowledge base and a sales page — and why B‑Class owners trust us.
Vetted Mercedes - Benz Specialists — Our network of 25+ vetted Mercedes-Benz specialists includes workshops that work on B‑Class OM651 injector‑seal failures every week — they're vetted specifically for diesel‑injector diagnosis and chain work, not generalists who happen to take on Mercedes jobs.
Part of Engine Finders - mercedesengine.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.
Data. Honesty. Specialists. All in one place.
Compare the W245 and W246 side‑by‑side, see the exact facelift changes and which engines sit in which generation.
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Not sure if your OM651 "Black Death" is terminal or just an injector seal? Our calculator will give you a personalised repair‑vs‑replace verdict.
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