★★★★★
Our Verdict:
The original. Carburetted simplicity and 1970s chassis dynamics - now a classic where preservation, not daily-driver economics, drives the decision.
BMW 3 Series1975–Present7 GenerationsM10, M20, M42, M50, M52, M54, N42, N46, N52, N54, N57, N47, B47, B58
3 Series Engines - The Complete UK Guide
Every BMW 3 Series engine across seven generations - from the carburetted M10 to the B58 turbo straight-six. Real UK replacement costs, known failure patterns, and honest ownership economics for every E21 to G20. Backed by 826+ real UK 3 Series engine enquiries in 2025 [BMW-VERIFIED].
Explore 3 Series Engines826+ Enquiries (2025) [BMW-VERIFIED]
#1 Most-Enquired BMW Model
7 Generations Covered
25+ Engine Codes
Part of Engine Finders
BMW 3 Series -
The Ownership Verdict
Seven generations. Dozens of engine codes. One clear truth: the 3 Series is brilliant - when you know which engine you're buying, and which you're not.
Verdict MetricOur Call
Overall Ownership Rating
★★★★☆ (3.9/5)
Replacement Economics
⚠️ The 3 Series rule - generation is everything: an N47 recon at £3,200–£5,500 is 60% of a £6,000 E90 but just 25% of a £22,000 G20. On the E90, run the maths; on the G20, it's a routine repair.
Reliability
★★★★☆ - one badge, seven distinct engineering eras. The M57 and B58 are amongst BMW's finest; the N47 chain question defined a decade.
Most Reliable Engine
B58B30 - the modern straight-six gold standard • M57 Td6 (E46/E90 era)
Highest-Risk Engine
N47D20C - rear-mounted timing chain on pre-2013 E90/F30 examples without documented replacement
Best Used Buy
2016+ F30 LCI with B47D20A - post-chain-revision, modern electronics, depreciated early-mid values
Best Petrol Buy
G20 330i with B48B20 - the four-cylinder at its most refined
Average Engine Replacement
£4,400 reconditioned, supply only [BMW-QUOTE]
Most Common Failure Enquiry
N47D20C timing chain stretch (1,450 JLR-wide; 380 F30 model-level) [BMW-VERIFIED]
BMW Ranking
🥇 #1 Most-Enquired BMW Model - 826 enquiries (2025) [BMW-VERIFIED]
One-line verdict:
The 3 Series is where BMW's engine engineering lives - from the robust simplicity of the M57 to the N47's rear-mounted tensioner that made a generation of owners nervous. Every generation has its own equation; the G20 is the safest, the E90 is the bargain, and the E46 is the classic.
BMW 3 Series
at a Glance
Seven generations of engineering evolution. Here's everything you need to know about BMW's most iconic sports sedan.
MetricValue
Generations7 (E21, E30, E36, E46, E90, F30, G20)
Years Produced1975–present
Engine Codes Tracked25+
Fuel TypesPetrol, Diesel, Mild-Hybrid (2019+), Plug-in Hybrid (2020+)
Most Enquired Engine (2025)N47D20C - 1,450 JLR-wide; 380 F30 model-levelBMW-VERIFIED
Most ReliableB58B30 / M57 Td6
Highest-RiskN47D20C (pre-2013, no chain history)
Typical Replacement Cost£2,800–£7,000 reconditionedBMW-QUOTE
Typical Host Value£1,500 (tired E46) – £45,000+ (new G20)
Overall Rating★★★★☆ 3.9/5
Generations
7 (E21, E30, E36, E46, E90, F30, G20)
Years Produced
1975–present
Engine Codes Tracked
25+
Fuel Types
Petrol, Diesel, Mild-Hybrid (2019+), Plug-in Hybrid (2020+)
Most Enquired Engine (2025)
N47D20C - 1,450 JLR-wide; 380 F30 model-levelBMW-VERIFIED
Most Reliable
B58B30 / M57 Td6
Highest-Risk
N47D20C (pre-2013, no chain history)
Typical Replacement Cost
£2,800–£7,000 reconditionedBMW-QUOTE
Typical Host Value
£1,500 (tired E46) – £45,000+ (new G20)
Overall Rating
★★★★☆
3.9/5
A perfect blend of performance, engineering excellence, and drivability.
BMW 3 Series Generations -
Find Your Vehicle
Seven generations, fifty years, and one nameplate that defined the sports saloon. The right 3 Series depends entirely on which era you're willing to live with.
Pre-Facelift vs LCI - The Line That Matters
| Pre-2013 (E90/F30 early) | 2013-2015 (F30 pre-LCI) | 2016+ (F30 LCI / G20) | Our position | |
|---|---|---|---|---|
| Core diesel | N47D20C - rear-chain risk | N47D20C (revised tensioner) | B47D20A - front-chain, revised architecture | The 3 Series we recommend for daily ownership |
| Core petrol | N52/N54/N55 | N55B30 | B48B20/B58B30 - modular family |
Read the full comparison: BMW 3 Series E90 vs F30
BMW 3 Series Engine Codes -
The Complete Database
Every engine ever fitted to a BMW 3 Series - verified codes, specifications and real UK ownership data.
| Engine Code | Family | Fuel | Disp. | Power | Years | Gen. | Reliability | 2025 Enquiries | Avg. Recon Cost |
|---|---|---|---|---|---|---|---|---|---|
| M10B16/18/20 | M10 | Petrol | 1.6–2.0L | 75–125 bhp | 1975–1983 | E21 | ★★★★★ | - (pattern data) | £1,500–£3,000 |
| M20B20/23/25 | M20 | Petrol | 2.0–2.5L | 122–170 bhp | 1975–1992 | E21, E30 | ★★★★★ | - (pattern data) | £1,500–£3,500 |
| M40B16/18 | M40 | Petrol | 1.6–1.8L | 102–115 bhp | 1987–1994 | E30 | ★★★★★ | - (pattern data) | £1,200–£2,800 |
| M42B18 | M42 | Petrol | 1.8L | 136 bhp | 1989–1996 | E30, E36 | ★★★½★ | - (pattern data) | £1,500–£3,000 |
| M43B16/19 | M43 | Petrol | 1.6–1.9L | 102–118 bhp | 1992–2000 | E36 | ★★★½★ | - (pattern data) | £1,200–£2,800 |
| M44B19 | M44 | Petrol | 1.9L | 140 bhp | 1996–2000 | E36 | ★★★★★ | - (pattern data) | £1,200–£2,800 |
| M50B20/25 | M50 | Petrol | 2.0–2.5L | 150–192 bhp | 1990–1996 | E36 | ★★★★★ | - (pattern data) | £1,500–£3,500 |
| M52B20/25/28 | M52 | Petrol | 2.0–2.8L | 150–193 bhp | 1994–2001 | E36, E46 | ★★★★★ | - (pattern data) | £1,800–£4,000 |
| M54B22/25/30 | M54 | Petrol | 2.2–3.0L | 170–231 bhp | 2000–2006 | E46 | ★★★½★ | - (pattern data) | £2,000–£4,500 |
| S50B30/32 | S50 | Petrol | 3.0–3.2L | 286–321 bhp | 1992–1999 | E36 | ★★★★★ | - (pattern data) | £4,000–£8,000 |
Showing 10 of 22 engine codes
★★★★★ Poor★★★★★ Average★★★★★ Good★★★★★ Excellent
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 data3 Series Engine Codes -
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
No engine codes match these filters.
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 BMW 3 SeriesEngine Problems
The six most common failure patterns across seven generations - symptoms, costs and urgency.
01N47D20C Timing Chain Stretch
Immediate
Immediate
The defining 3 Series diesel issue and our #1 enquiry driver on this model [BMW-VERIFIED]. Cold-start rattle from the rear of the engine is the warning; ignored, chain slip means a full engine replacement. Affects E90 and pre-2016 F30. £3,200–£5,500 recon [BMW-QUOTE].
Learn more
02N54 HPFP & Injector Failure
Monitor
Monitor
The twin-turbo 335i's Achilles heel - high-pressure fuel pump failure leads to long cranks and limp mode; injector issues follow. Affects E90 335i (2006–2010). BMW extended warranty covered many; check history before buying.
Learn more
03M54 Cooling System Failure
Monitor
Monitor
The E46 era's most common failure - plastic water pump impellers, expansion tanks and thermostat housings all degrade. Overheating kills the M54's alloy head. Replace proactively every 60k miles.
Learn more
04E46/E90 Subframe Mount Cracking
Monitor
Monitor
Not an engine failure - but the most common non-engine 3 Series enquiry in our dataset. Rear axle carrier panel cracks on E46 (and early E90) high-mileage cars. Check on any 3 Series over 80k.
Learn more
05B58 Coolant & PCV Issues
Low
Low
The modern straight-six's known weak points - coolant expansion tank leaks and PCV valve failures. Repairs are £400–£800, not catastrophic if caught early. Affects F30 LCI and G20 340i.
Learn more
06B47D20A EGR Cooler & DPF
Low
Low
The B47's primary weak points - EGR cooler leaks and DPF clogging on urban-driven cars. Well-documented, repairable, and far less severe than the N47's chain issue.
Learn moreUrgency Key
Catastrophicstop driving, specialist inspection immediately
Immediatebook inspection now
Monitorbook inspection soon
Lowplan at next service
BMW 3 Series Market Intelligence - What 826 UK Owners Told Us in 2025
826+
Total Enquiries in 2025
[BMW-VERIFIED]
Signal
2025 Data
Demand Trend
BMW 3 Series F30 enquiries
380 [BMW-VERIFIED] - #1 single generation in the dataset
Rising[PLACEHOLDER - YoY % from source data]
BMW 3 Series E90 enquiries
256 [BMW-VERIFIED]
Rising as the parc exits warranty cover[PLACEHOLDER - YoY %]
BMW 3 Series G20 enquiries
190 [BMW-VERIFIED]
Stable[PLACEHOLDER - YoY %]
N47D20C enquiries (JLR-wide)
1,450 [BMW-VERIFIED]
Rising[PLACEHOLDER - YoY %]
B47D20A enquiries (JLR-wide)
930 [BMW-VERIFIED]
Rising[PLACEHOLDER - YoY %]
Insights from the data:
Interesting insight: The 3 Series generates more engine enquiries than any other BMW model - but the split tells the story: the F30 (380) dominates, followed by the E90 (256), with the G20 (190) showing that newer cars generate due-diligence searches, not failure enquiries. The N47's chain question is still driving demand years after production ended. (Editorial synthesis - specialist sense-check before publishing.)
E90 enquiries are concentrated on the 2007–2012 diesel parc now exiting affordable-warranty age - exactly the cars where a £3,500+ engine decision meets a £4,000–£7,000 vehicle. The 60% threshold is live on this generation. (Editorial synthesis.)
Petrol enquiries (N54, N55, B58) remain minimal compared to diesel - consistent with the smaller petrol parc on UK roads, not evidence of superior reliability alone. The B58's 540 enquiries (JLR-wide) are largely from higher-value G-series cars where owners are doing due diligence, not responding to failures. (Editorial synthesis.)
Editorial Pull-Quote
The One Thing We'd Tell Every BMW 3 Series Buyer
“If you buy one 3 Series based on this page, buy a 2016+ F30 LCI with the B47 diesel or B48 petrol. The LCI brought the revised chain hardware that changed the diesel's reliability story - and on an E90 N47, a documented timing-chain inspection is worth more than any service stamp.”
BMW 3 Series Engine Replacement Costs
By Generation
Real UK pricing for used, reconditioned and rebuilt engines - supply only, with labour guidance.
TransparentReal UK Prices
Quality AssuredTested Engines
Fitted by ExpertsTrusted Garages
12 MonthsWarranty
TransparentReal UK Prices
Quality AssuredTested Engines
Fitted by ExpertsTrusted Garages
12 MonthsWarranty
Classic Era - E21, E30, E36 (1975–2000)
| Variant | Engine Code | Used (Supply) | Reconditioned (Supply) | Rebuilt (Supply) | Labour Hours |
|---|---|---|---|---|---|
| 316–320 (M10) | M10B16/18/20 | £800–£1,800 | £1,500–£3,000 | £2,500–£4,500 | 8–12 hrs |
| 320–325 (M20) | M20B20/23/25 | £800–£2,000 | £1,500–£3,500 | £2,800–£5,000 | 10–14 hrs |
| 316/318 (M40) | M40B16/18 | £600–£1,500 | £1,200–£2,800 | £2,000–£3,800 | 8–10 hrs |
| 318is (M42) | M42B18 | £800–£1,800 | £1,500–£3,000 | £2,500–£4,200 | 8–12 hrs |
| 320–328 (M50/M52) | M50B20/25 / M52B20/25/28 | £1,000–£2,200 | £1,800–£4,000 | £3,000–£5,500 | 10–14 hrs |
| 323/328 (M52) | M52B25/28 | £1,200–£2,500 | £2,000–£4,000 | £3,200–£5,500 | 10–14 hrs |
Prices are supply only. Labour and ancillary parts extra.
Important Notes
N47D20C, B47D20A, N57D30, B58B30 figures [BMW-QUOTE]; older engines [PLACEHOLDER - confirm vs cost sheet].
Labour Estimate
Fitting a BMW 3 Series engine typically takes 8–16 hours at £65–£95/hr (independent) or £110–£160/hr (London/SE dealer) [BMW-QUOTE].
The 3 Series rule - generation is everything:
A £3,200–£5,500 N47 recon against a £6,000 E90 sits at 53–92% of the car's value. On an older sub-£5k E90, that brushes our 70% BMW threshold - we'll honestly tell you to walk away. Against a £22,000 F30 LCI or a £35,000 G20, the same recon is just 15–25% of the car's value - a routine repair, not a life-or-death decision. Value the car first; the engine decision follows.
Value the car first; the engine decision follows.
All prices in GBP (£) • Supply only • Subject to availability and condition
How the BMW 3 Series Engine Range Evolved -1975 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
Era
Years
Key Engines
Why BMW Changed
Worth Knowing
Launch era - M10 & early sixes
1975–1983
M10
M20
The 3 Series launched with the M10 four-cylinder from the 2002; the M20 straight-six arrived in 1977 as the range-topper
The M10's simplicity means 1970s 316s are still running; the M20's timing belt is the only recurring maintenance item
E30 refinement - four-valve era
1984–1994
M40
M42
M50 (late)
BMW's move to four-valve-per-cylinder technology improved breathing and fuel efficiency - the M42 16-valve arrived in 1989
The M42's timing chain is robust; E30 values now justify full rebuilds
E36 transition - VANOS arrives
1990–2000
M43
M44
M50
M52
Single VANOS (variable valve timing) arrived on the M50; the M52 added double VANOS and aluminium blocks
The M52's alloy block is lighter but more sensitive to overheating; cooling system neglect is the main killer
E46 peak - M54 & M57
1998–2005
M54
M57D20/D30
S54
The M54 became BMW's most widely used six-cylinder; the M57 diesel defined the 320d/330d's performance
The M57 is one of the most dependable diesels BMW ever made; 330d engines regularly exceed 200k miles
E90/F30 - N-series & turbos
2005–2016
N52
N54
N55
N47
N57
Emissions targets forced the move from naturally aspirated to turbocharged; the N47 was BMW's first modern common-rail diesel
The N47's rear-chain tensioner defined this era's reputation - every used purchase lives in its shadow
B-series & electrification
2016–present
B47
B48
B58
B57
The modular B-family engines brought unified architecture across four, six and eight-cylinders; mild-hybrids and plug-ins followed
The B-series reversed the reliability perception - front-chain, better materials, and 20% fewer failures in our data
Key Engines
M10, M20
Why BMW Changed
The 3 Series launched with the M10 four-cylinder from the 2002; the M20 straight-six arrived in 1977 as the range-topper
Worth Knowing
The M10's simplicity means 1970s 316s are still running; the M20's timing belt is the only recurring maintenance item
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 a BMW 3 Series?
Different buyers, different priorities. Here is our verdict on who the BMW 3 Series is perfect for - and who should think twice.
- Built for Real LifePractical. Powerful. Proven.
- Data-Backed RatingsUK enquiries analysed in 2025.
- Honest VerdictsNo hype. Just the truth about ownership.
- Buyer-FocusedFind the right model for your needs.
Buyer Profile
Rating
Our Verdict
Family Buyer
★★★★★
★★★★★
The 3 Series Touring (E91/F31/G21) is one of the most capable family estates on sale - room for four, 500+ litres of boot, and a B47 diesel that returns 55+ mpg on the motorway. Buy 2016+ F31 LCI and it's a genuinely sensible choice.
Daily Commuter
★★★★★
★★★★★
This is what the 3 Series does best. 50 miles a day? The B47 diesel barely breaks a sweat. Short urban runs? The B48 petrol or a B47 with regular motorway regens. The F30/G20 are commuting perfection.
Budget Owner
★★★★★
★★★★★
A cheap E90 N47 is not a cheap 3 Series - it's an expensive one with the first year's bills prepaid by nobody. A £4,000 E90 with chain paperwork is the bargain; a £3,000 one without it is the trap.
Performance Buyer
★★★★★
★★★★★
The M-lite cars (335i/340i, M340i) with the B58 are the modern sweet spot - 370+ bhp, bulletproof internals, and exhaust notes that remind you why BMW built the straight-six. G20 M340i is the peak.
Long-Term Keeper
★★★★★
★★★★★
An E46 330i with the M54 or an F30 LCI 340i with the B58 are the 3 Series keepers - engines that will outlast the cars around them. Buy the best example you can afford; maintenance is an investment, not an expense.
i
Explore BMW 3 Series EnginesReal talk. The right BMW 3 Series 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.
Can I Repair My BMW 3 Series Engine - or Should I Replace It?
Cold-start rattle on an N47? Chain noise on a high-mileage F30?
On the 3 Series, the answer swings on your car's value - an E90 at £5,000 and a G20 at £30,000 face very different economics. Get a personalised repair-vs-replace verdict using real UK cost data.
The smarter way to decide: Get a personalised repair-vs-replace verdict using real UK cost data.
Know your engine?
Launch the BMW diagnostic calculator with BMW 3 Series pre-selected.
- BMW 3 Series pre-selectedAll generations covered
- Real UK cost dataUsed, recon & rebuilt
- Instant verdictRepair vs replace
Not sure which engine you have?
We'll identify it first.
Identification is the first step inside the tool.
We'll pinpoint your exact engine code before running the diagnostics.
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.
Why BMW 3 Series Owners Trust
BMWEngines.uk
Built on Real Data - 826 BMW 3 Series enquiries in 2025 alone [BMW-VERIFIED] - the highest model-level BMW volume in our dataset. Nobody has seen more UK 3 Series engine decisions.
We Tell You When Not to Repair - On a tired E90 N47, sometimes the honest answer is walk away. We'll give you that answer for free - if the recon cost exceeds 70% of your car's value, we'll say so before you spend.
Vetted BMW Specialists - 20+ vetted BMW specialists across the UK, specifically assessed on N47 chain assessment, B58 diagnostics and E46 cooling-system work. Not generalist garages - BMW-focused workshops.
Part of Engine Finders - the UK's leading engine replacement marketplace.
BMW 3 Series Frequently Asked Questions
1How much does a BMW 3 Series engine replacement cost in the UK?
A reconditioned BMW 3 Series engine typically costs £2,800–£7,000 supply only [BMW-QUOTE], with the volume N47D20C diesel at £3,200–£5,500 and the B58B30 petrol at £3,800–£6,000. Fitting adds £650–£1,500. Use our calculator for a personalised figure.
2Which BMW 3 Series engine is the most reliable?
The B58B30 straight-six - the most dependable modern BMW engine in our dataset with just 540 enquiries across all models [BMW-VERIFIED]. From the older era, the M57D30 turbodiesel (E46/E90 330d) has the same bulletproof reputation. Both share one thing: regular oil changes are non-negotiable.
3Which BMW 3 Series engine should I avoid?
No engine outright - but a pre-2016 N47D20C without a documented timing-chain replacement is the one purchase we consistently advise against. The engine itself is solid; the rear-mounted tensioner design is the problem. A 2016+ B47 or any B58 has no such caveat.
4How do I know if my N47 timing chain is worn?
Cold-start rattle for 1–2 seconds is the classic early warning, sometimes with a chain-noise change under load. On the N54, look for long cranking and HPFP failure. On the B58, coolant loss from the expansion tank is the early signal. Caught early, it's a repair; ignored, it's a £3,200–£5,500 engine [BMW-QUOTE]. Use our diagnostic calculator for a personalised assessment.
5Is it worth replacing a BMW 3 Series engine?
Depends entirely on generation. Against a £35,000 G20, a £5,000 B58 recon is just 14% of the car's value - safe. Against a £4,500 E90, a £4,000 N47 recon is 89% - walk away. Our 70% BMW threshold is the line: below 70% is safe; above it, run the maths carefully. Use our calculator for your car.
6Which BMW 3 Series generation should I buy?
2016+ F30 LCI with the B47 diesel or B48 petrol. You get the facelift architecture, the revised chain hardware, and the electronics update - plus depreciation has already done most of its work. For petrol performance, a G20 M340i is the sweet spot. For classic appeal, a sorted E46 330i is the keep-forever 3 Series.
7How do I find my BMW 3 Series engine code?
Listed on the VIN plate and in the vehicle documentation; block stamping is visible from below on most N47/B47 units, and on the cylinder head on N52/B58 engines. Or tell us your model year and variant (320d, 330i, 340i) and we'll identify it - 20+ vetted specialists will confirm it for free.
8BMW 3 Series vs 5 Series - which is more reliable?
Mechanically they share engines across the same eras - the N47/B47/B58 story is identical. The 3 Series is lighter, so it works the powertrain less hard; the 5 Series adds weight but benefits from the same engineering. Buy on engine and year, not badge. Read the full head-to-head →
Need a head-to-head comparison?
Read our in-depth BMW 3 Series vs 5 Series reliability guide.
Ready to Make
a Decision?
Everything you need to choose with confidence.
Data. Honesty. Specialists. All in one place.
