The Most Reliable BMW Engines, Ranked (Bimmer.AI Reliability Scores)
Every major BMW engine on the UK used market, scored out of 10 and ranked best to worst. The B58, B57, S58 and S68 lead; the N47, N62 and N63 sit at the bottom for reasons worth understanding before you buy.
Quick answer
If you want the safest used BMW engine, buy a B58 petrol or a B57 diesel (both 8/10). The cheapest engines to live with are the modern straight-sixes; the most expensive surprises hide in the older V8s (N62, N63) and the early small diesels (N47). But remember: a well-kept example of a mid-table engine beats a neglected example of a top one. Service history beats engine choice.
The ranking, best to worst
The score is the Bimmer.AI reliability score, our own editorial metric. It weighs the severity of each engine's known failure modes against how often they occur, then factors typical UK repair exposure, jobs that need the engine or gearbox out, and faults that recur, drag a score down. It is not an official BMW figure and not a third-party reliability index. Treat it as a shortlisting filter, then judge the specific car.
| # | Engine | Type | Years | Score | Why this score |
|---|---|---|---|---|---|
| 1 | BMW B58 | 3.0L straight-six petrol turbo | 2015 to present | 8/10 | BMW's modern petrol benchmark. Closed-deck block, robust internals, no chronic chain or oil-consumption story. ULEZ compliant. |
| 2 | BMW B57 | 3.0L straight-six diesel turbo | 2017 to present | 8/10 | The strongest, cleanest diesel BMW has built. Resolved the N57 weak points; Euro 6 and ULEZ compliant. Verify AdBlue/SCR health. |
| 3 | BMW S58 | 3.0L straight-six petrol turbo (M) | 2019 to present | 8/10 | Current M3/M4/X3 M engine. Closed-deck B58-derived block engineered out the S55 crank-hub anxiety. The reliable way into a fast M car. |
| 4 | BMW S68 | 4.4L V8 petrol twin-turbo (M) | 2022 to present | 8/10 | Phase 1 of BMW's latest M V8 (X5 M, XM, M5 era). Too new for a long failure record, but a clean-sheet design with no chronic fault yet. |
| 5 | BMW N57 | 3.0L straight-six diesel turbo | 2008 to 2017 | 7/10 | One of BMW's finest diesels in single-turbo 330d/530d form. Avoid the tri-turbo N57S (535d) where actuator failures are common. |
| 6 | BMW B48 | 2.0L four-cylinder petrol turbo | 2014 to present | 7/10 | The sensible modern four-pot petrol. Fixed the N20 timing-chain weakness. Watch oil-filter-housing gasket leaks on higher miles. |
| 7 | BMW N55 | 3.0L straight-six petrol turbo | 2010 to 2018 | 7/10 | Single-turbo six that smoothed out the N54's rough edges. Watch the water pump, charge-pipe and VANOS solenoids; otherwise stout. |
| 8 | BMW S55 | 3.0L straight-six petrol turbo (M) | 2014 to 2020 | 7/10 | F80 M3 / F82 M4 engine. Fast and tuneable, but rod bearings and crank-hub slip are the known M-car liabilities to budget for. |
| 9 | BMW S65 | 4.0L V8 petrol (M) | 2007 to 2013 | 7/10 | The naturally aspirated E9x M3 V8. A genuine modern classic, but rod bearings and throttle-actuator failures define the ownership risk. |
| 10 | BMW B47 | 2.0L four-cylinder diesel turbo | 2014 to present | 6/10 | N47's successor. Timing-chain concern largely resolved post-2017; Euro 6 and ULEZ compliant. Confirm the EGR fire-risk recall is done. |
| 11 | BMW N20 | 2.0L four-cylinder petrol turbo | 2011 to 2017 | 6/10 | Capable engine undone by a timing-chain weakness on pre-2015 builds. A documented chain replacement turns a worry into a fair buy. |
| 12 | BMW N54 | 3.0L straight-six petrol twin-turbo | 2006 to 2013 | 6/10 | The tuning legend. HPFP recall, wastegate rattle and injector wear are the trade-offs for huge headroom. A project, not an appliance. |
| 13 | BMW S63 | 4.4L V8 petrol twin-turbo (M) | 2009 to present | 6/10 | Hot-vee M5/M6/X5 M V8. Immense performance, but rod bearings, timing components and turbo oil feeds carry real repair exposure. |
| 14 | BMW S85 | 5.0L V10 petrol (M) | 2005 to 2010 | 6/10 | The E60 M5 / E63 M6 V10. Spectacular, but rod bearings, VANOS and the SMG actuator make it a heart-over-head ownership case. |
| 15 | BMW N47 | 2.0L four-cylinder diesel turbo | 2007 to 2014 | 5/10 | The famous timing-chain engine, worse on pre-2011 rear-chain builds. Euro 5, not ULEZ compliant. Price the chain risk in explicitly. |
| 16 | BMW N62 | 4.4 to 4.8L V8 petrol | 2002 to 2010 | 5/10 | Valve-stem seals (the smoking-on-startup V8), alternator bracket gasket and coolant pipe failures make this a high-maintenance V8. |
| 17 | BMW N63 | 4.4L V8 petrol twin-turbo | 2008 to present | 5/10 | Hot-vee layout cooks ancillaries: oil consumption, coolant transfer pipe (engine-out) and timing wear. The riskiest used BMW V8. |
Scores: 8/10 strong · 6 to 7/10 solid with caveats · 5/10 buy with eyes open. Click any engine to open its full reliability guide.
The standouts (8/10)
Four engines top the table. They share a pattern: modern design, closed-deck or otherwise strengthened blocks, and no single chronic failure that defines ownership.
B58 petrol, the all-round pick
The B58 3.0-litre straight-six is the engine to buy if you can. Fitted to the M140i, M240i, 340i, 440i, 540i and Z4 M40i, it pairs serious performance with a robustness the older sixes never had. No timing-chain fear, no oil-consumption story, comfortably ULEZ compliant. The main jobs are routine: water pump and the odd charge-pipe over time. For most buyers it is the obvious answer.
B57 diesel, the long-haul choice
The B57 3.0-litre straight-six diesel is the strongest, cleanest diesel BMW has built, fitted to 30d models from 2017. It engineered out the N57's weak spots and is Euro 6 / ULEZ compliant. If you cover high motorway mileage, this is the engine. The one check that matters on a used example is AdBlue / SCR system health.
S58 and S68, the reliable M route
The S58 is the current M3 / M4 / X3 M engine, a closed-deck, B58-derived six that designed out the crank-hub anxiety that haunts the older S55. The S68 is BMW's latest M V8 (X5 M, XM, the new M5 era); it is too new for a long field record, but it is a clean-sheet design with no chronic fault yet identified. Both are the sensible way into a fast modern M car.
Solid with caveats (6 to 7/10)
The mid-table is where most of the used market actually sits. These engines are good buys with one or two known liabilities you price in rather than fear.
- N57 (7/10): superb in single-turbo 330d / 530d form. The trap is the tri-turbo N57S in the 535d, where turbo-actuator failures are common and expensive.
- B48 (7/10): the modern 2.0 petrol that fixed the N20 chain weakness. Keep an eye on oil-filter-housing gasket leaks at higher miles.
- N55 (7/10): the single-turbo six that smoothed out the N54. Water pump, charge-pipe and VANOS solenoids are the usual jobs.
- S55 (7/10): the F80 M3 / F82 M4 engine. Fast and tuneable, but budget for rod bearings and watch for crank-hub slip.
- S65 (7/10): the naturally aspirated E9x M3 V8 and a modern classic, defined by rod bearings and throttle-actuator failures.
- B47 (6/10): N47's successor, ULEZ compliant, with the chain concern largely resolved post-2017. Confirm the EGR fire-risk recall is done.
- N20 (6/10): a capable engine undone by a pre-2015 timing-chain weakness. A documented chain replacement makes it a fair buy.
- N54 (6/10): the twin-turbo tuning legend. HPFP recall, wastegate rattle and injectors are the price of its headroom. A project, not an appliance.
- S63 (6/10) and S85 (6/10): the hot-vee M5 V8 and the E60 M5 V10. Spectacular engines, heart-over-head ownership, real repair exposure.
Buy with your eyes open (5/10)
The three lowest scorers are not un-buyable. They are engines where a specific, well-known failure mode carries enough UK repair exposure that you must inspect carefully and negotiate accordingly.
| Engine | The defining risk | Indicative UK exposure |
|---|---|---|
| N47 diesel | Timing chain stretch / failure, worse on pre-2011 rear-chain builds. Euro 5, not ULEZ. | £1,500 to £2,500 |
| N62 V8 | Valve-stem seals (smoke on startup), coolant transfer pipe, alternator bracket gasket. | £1,500 to £3,500 |
| N63 V8 twin-turbo | Oil consumption, coolant transfer pipe (engine-out job), timing and turbo wear. | £2,500 to £6,000+ |
For the N47, the single most-searched BMW reliability issue, read the dedicated N47 timing-chain buyer guide before you view a car. On the V8s, a borescope and a careful cold-start are non-negotiable.
Reliability is about the car, not just the engine
The biggest mistake buyers make with a ranking like this is treating the engine score as the whole story. It is not. A neglected B58 with skipped oil changes and a botched remap is a worse buy than a fastidiously maintained N47 with a documented chain replacement and a full service book.
The score tells you the baseline risk of the engine family. The individual car tells you how much of that risk has actually been managed. What separates a good used BMW from a bad one, on the same engine, is almost always:
- Oil-change discipline. Shorter-than-BMW intervals (every 9,000 to 12,000 miles, not the long "lifetime" fills) protect chains, turbos and bearings. See the routine in our BMW running costs guide.
- Completed recalls. The EGR fire-risk recall on N47 / B47 diesels is the headline one; verify it at gov.uk by VIN.
- Honest service history. BMW-dealer or known indie specialist stamps, no gaps over the danger-window mileage.
- Gearbox care. The ZF 8-speed auto is excellent but not truly "sealed for life"; a fluid-and-filter change around 60,000 to 80,000 miles keeps shifts crisp.
Use the ranking to shortlist, then judge the specific car on its paperwork and a proper pre-purchase inspection.
Diesel or petrol? It depends on your miles
The two best engines in the table are one of each: a petrol B58 and a diesel B57. The right choice is about use, not just reliability. High annual motorway mileage favours the B57 diesel on running costs and DPF health; mixed or low urban mileage favours a petrol like the B58 or B48, which avoids DPF clogging and short-journey diesel abuse. ULEZ also bites harder on diesel: only Euro 6 (broadly late 2015 onwards) diesels comply, while almost all petrols from 2006 do. Our diesel vs petrol guide works through the trade-off in full.
Check the engine in a real listing
Paste any BMW listing, VIN, or reg plate. Bimmer.AI identifies the exact engine, pulls its failure patterns and reliability score, and returns a buy/negotiate/walk verdict in about 30 seconds.
Run a Bimmer.AI buyer report →The Bimmer.AI reliability score is our own editorial metric, severity multiplied by frequency of known failures, weighted by UK repair exposure. It is not an official BMW figure or a third-party reliability index, and it describes the engine family, not any individual car. Repair-cost ranges are indicative UK figures that vary by region, specialist, and parts supply. Always pair this view with a physical inspection and a vehicle-history check.
Frequently asked questions
What is the most reliable BMW engine?
By the Bimmer.AI reliability score the joint leaders are the B58 (3.0 straight-six petrol), the B57 (3.0 straight-six diesel), the S58 (M-car straight-six) and the S68 (M V8), each scoring 8 out of 10. The B58 is the all-round pick for most buyers: it is widely fitted, ULEZ compliant and has no chronic timing-chain or oil-consumption story. The B57 is the diesel equivalent if you cover high motorway mileage.
What is the most reliable BMW diesel engine?
The B57 3.0-litre straight-six diesel, fitted to 30d models from 2017, scores 8 out of 10 and is the strongest diesel BMW has made. It resolved the weak points of the older N57 and is Euro 6 / ULEZ compliant. The single-turbo N57 (330d, 530d) is the next best at 7 out of 10. Avoid the tri-turbo N57S (535d), where turbo-actuator failures are common.
What is the most reliable BMW petrol engine?
The B58 3.0-litre straight-six petrol, scoring 8 out of 10, fitted to cars like the M140i, M240i, 340i, 440i and Z4 M40i. It has a closed-deck block, robust internals and an excellent tuning headroom without the fragility of older sixes. The four-cylinder B48 (7 out of 10) is the sensible smaller-capacity choice.
What are the BMW engines to avoid?
The lowest-scoring engines in the Bimmer.AI database are the N47 diesel, the N62 V8 and the N63 V8, each at 5 out of 10. The N47 has a timing-chain weakness (worse on pre-2011 builds), the N62 suffers valve-stem-seal and coolant-pipe failures, and the N63 hot-vee V8 has oil consumption and an engine-out coolant transfer pipe job. None are un-buyable, but each carries real UK repair exposure that has to be priced in.
How are the Bimmer.AI reliability scores calculated?
The score is Bimmer.AI's own editorial metric, not an official BMW figure or a third-party reliability index. It weighs the severity of an engine's known failure modes against how frequently they occur, then factors the typical UK repair exposure (engine-out jobs and recurring faults score worse). It is a starting filter for comparing engines, not a guarantee about any individual car.
Is a higher-mileage BMW with the right engine better than a low-mileage one with a weak engine?
Often, yes. A well-serviced B57 or B58 at 90,000 miles with a full history is a safer buy than a neglected N47 or N63 at 40,000 miles. Reliability is about the specific car as much as the engine family: documented oil changes, completed recalls and an honest service record beat engine choice alone. Use the score to shortlist, then judge the individual car.
Are the most reliable BMW engines also ULEZ compliant?
Mostly. The top-scoring petrols (B58, S58, S68, B48, N55) are comfortably ULEZ compliant, as petrol broadly needs to be Euro 4 (2006 onwards). On diesel, only Euro 6 cars (broadly late 2015 onwards) are compliant, so the B57 and B47 qualify while the older N47 and N57 generally do not. Always confirm the specific car on the TfL checker by registration, as compliance is per-vehicle.
Does a reliable engine mean the whole BMW is reliable?
No. The engine is the biggest single risk on a used BMW, but the gearbox, cooling system, electronics and suspension all carry their own costs. A strong engine score removes the largest worry, not all of them. Pair the engine view with the relevant chassis guide and a proper pre-purchase inspection before you commit.