How much does a BMW 8 Series G14 powertrain replacement cost in the UK?

A reconditioned G14 powertrain costs between £4,500 and £14,000 supply-only, depending on the engine -the B58 six-cylinder ranges £4,800–£8,000, the N63 V8 runs £6,000–£10,000, and the S63 M8 Competition engine runs £8,000–£14,000. Fitting adds 12–24 hours of labour at £65–£90/hr. Use our calculator for a personalised quote.

Which BMW 8 Series G14 powertrain is the most reliable?

The B58B30 3.0-litre six-cylinder (840i) is widely regarded as BMW's most reliable modern six-cylinder -proven durability, no major design flaws, and only minor HPFP and cooling system maintenance required. On diesel, the B57D30B (840d) is also highly reliable, with timing chain issues described as 'exceedingly rare.'

What are the common problems with the BMW 8 Series G14?

Valve stem seal wear on the N63 V8 (M850i) and S63 V8 (M8 Competition), high-pressure fuel pump (HPFP) failure on the B58 (840i), and DPF blockage on the B57 diesel (840d) used predominantly for urban driving. The G14 also suffers from folding roof mechanism wear and electrical system issues on higher-spec models.

Is the BMW 8 Series G14 reliable?

It depends heavily on the powertrain. The B58 six-cylinder is highly reliable. The N63/S63 V8s are more demanding -they are high-performance engines that require meticulous maintenance. For any G14, a thorough inspection and maintenance history check are essential, particularly on V8 models.

Which BMW 8 Series G14 powertrain should I avoid?

Early N63 V8 (2018–2020 M850i) without documented valve stem seal work carries the highest risk. Also avoid any B57 diesel without documented DPF maintenance history. If you must have a V8, choose a 2020+ N63B44T3 with full service history and budget for valve stem seals at 40,000–60,000 miles.

How do I know if my G14 powertrain needs replacing?

Blue smoke on startup (N63/S63 valve stem seals), long cranking or power loss (B58 HPFP), DPF warning lights on diesel, or persistent rough running on any high-mileage unit are the key warning signs. Use our diagnostic tool for a personalised assessment.

Is it worth replacing a BMW 8 Series G14 powertrain, or should I scrap the car?

Apply the 70% BMW scrap threshold -but this is a £30,000+ car, so value assessment differs. Against a well-kept £40,000 G14, a £6,000 N63 recon is 15% of the car's value -safe. Against a tired £30,000 early example, the same recon is 20% -still safe. For sub-£25,000 examples, evaluate carefully.

How long do BMW 8 Series G14 powertrains last?

The B58 can comfortably exceed 150,000 miles with routine maintenance. The B57 diesel is equally durable, with 200,000+ miles achievable with proper servicing. The N63/S63 V8s require more frequent maintenance -valve stem seals are a known wear item at 40,000–60,000 miles.

What is the difference between the G14 and other 8 Series variants?

The G14 is the convertible variant of the second-generation 8 Series. The G15 is the two-door coupé, the G16 is the four-door Gran Coupé, and the G14 is the folding-roof convertible. All three share the same CLAR platform and powertrain options. The G14 succeeds the F12 6 Series Convertible (2011–2018).

How do I find my BMW 8 Series G14 powertrain code?

The powertrain code is listed on the VIN plate, vehicle documentation, and on a sticker under the bonnet. For 3.0 petrol, look for B58B30C (pre-LCI 840i) or B58B30M1 (LCI 840i). For 4.4 V8, look for N63B44D (pre-LCI M850i) or N63B44T3 (LCI M850i). For M8, look for S63B44B (pre-LCI) or S63B44T4 (LCI). For diesel, look for B57D30B (840d). Tell us your variant and year, and we'll confirm.

G14 Powertrain Cost UK -Compare Quotes

Name: BMW 8 Series G14 UK Enquiry Data 2025
Creator: bmwengines.uk

BMW 8 Series G14 Powertrain Codes -The Complete Database

Every powertrain fitted to the G14 8 Series Convertible specifically -from the 2018 launch through the LCI facelift and the introduction of the M8 Competition.

Engine CodeFamilyFuelDisplacementPowerYears (G14)Variants (badges)Reliability2025 EnquiriesAvg. Recon Cost

B58B30CB58 TUPetrol, turbo I63.0L (2998cc)245 kW (333 hp)2018–2020840i, 840i xDrive★★★★☆ [PROVISIONAL]-(pattern data)£4,800–£8,000

B58B30M1B58 TU2Petrol, turbo I63.0L (2998cc)250 kW (335 hp)2020–2026840i, 840i xDrive★★★★☆ [PROVISIONAL]-(pattern data)£4,800–£8,000

N63B44DN63 TU3Petrol, twin-turbo V84.4L (4395cc)390 kW (530 hp)2018–2020M850i xDrive★★★☆☆ [PROVISIONAL]-(pattern data)£6,000–£10,000

N63B44T3N63 TU3Petrol, twin-turbo V84.4L (4395cc)390 kW (530 hp)2020–2026M850i xDrive★★★☆☆ [PROVISIONAL]-(pattern data)£6,000–£10,000

S63B44BS63Petrol, twin-turbo V84.4L (4395cc)460 kW (625 hp)2019–2022M8 Competition★★★☆☆ [PROVISIONAL]-(pattern data)£8,000–£14,000

S63B44T4S63Petrol, twin-turbo V84.4L (4395cc)460 kW (625 hp)2022–2026M8 Competition★★★☆☆ [PROVISIONAL]-(pattern data)£8,000–£14,000

B57D30BB57Diesel, twin-turbo I6 MHEV3.0L (2993cc)235–250 kW (315–340 hp)2019–2026840d xDrive★★★★☆ [PROVISIONAL]-(pattern data)£4,500–£7,500

Engine CodeFuelPowerYearsReliabilityEnquiriesAvg. Recon Cost

B58B30CB58 TUPetrol, turbo I6245 kW (333 hp)2018–2020★★★★☆ [PROVISIONAL]-(pattern data)£4,800–£8,000

B58B30M1B58 TU2Petrol, turbo I6250 kW (335 hp)2020–2026★★★★☆ [PROVISIONAL]-(pattern data)£4,800–£8,000

N63B44DN63 TU3Petrol, twin-turbo V8390 kW (530 hp)2018–2020★★★☆☆ [PROVISIONAL]-(pattern data)£6,000–£10,000

N63B44T3N63 TU3Petrol, twin-turbo V8390 kW (530 hp)2020–2026★★★☆☆ [PROVISIONAL]-(pattern data)£6,000–£10,000

S63B44BS63Petrol, twin-turbo V8460 kW (625 hp)2019–2022★★★☆☆ [PROVISIONAL]-(pattern data)£8,000–£14,000

S63B44T4S63Petrol, twin-turbo V8460 kW (625 hp)2022–2026★★★☆☆ [PROVISIONAL]-(pattern data)£8,000–£14,000

B57D30BB57Diesel, twin-turbo I6 MHEV235–250 kW (315–340 hp)2019–2026★★★★☆ [PROVISIONAL]-(pattern data)£4,500–£7,500

Overview

BMW 8 Series G14 -Overview

The BMW G14 is the convertible variant of the second-generation BMW 8 Series, a range of grand tourers produced since 2018.

Launched in November 2018, the G14 features a folding cloth roof that operates in 15 seconds at speeds up to 50 km/h (31 mph). Built on BMW's CLAR platform, the G14 shares its powertrain line-up with the G15 Coupé and G16 Gran Coupé. The engine range includes the 3.0-litre B58 six-cylinder petrol (840i), the 4.4-litre N63 V8 petrol (M850i xDrive), the high-performance S63 V8 (M8 Competition), and the 3.0-litre B57 six-cylinder diesel (840d xDrive), all mated to an 8-speed automatic transmission. An LCI facelift in 2020 introduced updated engines and mild-hybrid technology on the diesel variant. The 8 Series range is scheduled to end production in 2026.

Key Facts

Platform

BMW CLAR (Cluster Architecture)

Predecessor

BMW 6 Series Convertible (F12)

Successor

None (production ends 2026)

Sibling body styles

G15 Coupé, G16 Gran Coupé

Market Intelligence

The G14 8 Series Convertible is a low-volume luxury grand tourer; enquiries are concentrated on the B58 six-cylinder and N63 V8 petrol engines, with values ranging from £35,000 for early 840i examples to £80,000+ for well-specced M8 Competitions.

BMW 8 Series G14 -Overview

The BMW G14 is the convertible variant of the second-generation BMW 8 Series, a range of grand tourers produced since 2018.

Launched in November 2018, the G14 features a folding cloth roof that operates in 15 seconds at speeds up to 50 km/h (31 mph). Built on BMW's CLAR platform, the G14 shares its powertrain line-up with the G15 Coupé and G16 Gran Coupé. The engine range includes the 3.0-litre B58 six-cylinder petrol (840i), the 4.4-litre N63 V8 petrol (M850i xDrive), the high-performance S63 V8 (M8 Competition), and the 3.0-litre B57 six-cylinder diesel (840d xDrive), all mated to an 8-speed automatic transmission. An LCI facelift in 2020 introduced updated engines and mild-hybrid technology on the diesel variant. The 8 Series range is scheduled to end production in 2026.

Key Facts

Platform

BMW CLAR (Cluster Architecture)

Predecessor

BMW 6 Series Convertible (F12)

Successor

None (production ends 2026)

Sibling body styles

G15 Coupé, G16 Gran Coupé

Market Intelligence

The G14 8 Series Convertible is a low-volume luxury grand tourer; enquiries are concentrated on the B58 six-cylinder and N63 V8 petrol engines, with values ranging from £35,000 for early 840i examples to £80,000+ for well-specced M8 Competitions.

Best & Worst Engines

Best Petrol Overall

B58B30M1 3.0-litre six-cylinder (840i) -The 335 bhp B58 is widely regarded as BMW's most reliable modern six-cylinder. Delivering 500 Nm of torque and 0-62 in approximately 5.2 seconds, it offers genuine grand touring performance with proven durability. The TU2 version (2020+) adds mild improvements without compromising reliability.

“”

Who it's for: buyers who want the sweet spot of performance, refinement, and reliability.

Best Diesel Overall

B57D30B 3.0-litre six-cylinder (840d xDrive) -The 315–340 bhp B57 six-cylinder diesel delivers effortless torque (680–700 Nm), excellent refinement, and genuine durability for high-mileage grand touring. The mild-hybrid system adds efficiency without complexity.

“”

Who it's for: high-mileage buyers who want effortless torque and 40+ mpg economy.

Highest Risk

N63B44D/N63B44T3 4.4-litre V8 (M850i xDrive) -The hot-vee V8 design places turbochargers in the engine's 'V', generating significant heat. Valve stem seal wear and cooling system leaks are well-documented on N63-family engines. The updated TU3 version (2020+) is improved but still demands meticulous maintenance.

“”

Who it's for: buyers who accept the premium and keep the car under warranty.

Most Expensive Failure

S63B44B/S63B44T4 4.4-litre V8 (M8 Competition) -The 625 bhp S63 is the most expensive powertrain in the G14 line-up to replace, with reconditioned units costing £8,000–£14,000. The high-performance V8 shares the N63's hot-vee architecture with additional stresses from higher boost and output.

“”

Who it's for: collectors and enthusiasts who accept the premium.

Best Value

B58B30M1 3.0-litre six-cylinder (840i) -The 335 bhp B58 offers the best balance of performance, refinement, and running costs. It's the most common G14 engine, parts are widely available, and the recon cost is significantly lower than the V8 options.

“”

Who it's for: the majority of G14 buyers who want genuine grand touring performance without V8 running costs.

Most Overlooked

B57D30B 3.0-litre diesel (840d xDrive) -Often overlooked by buyers who default to the petrol six or V8, the 840d delivers effortless torque, 40+ mpg economy, and genuine long-distance capability. With 680 Nm of torque and 0-62 in approximately 5.1 seconds, it's the ultimate motorway cruiser in the G14 range.

“”

Who it's for: buyers who prioritise long-distance touring economy without sacrificing performance.

Best Petrol Overall

B58B30M1 3.0-litre six-cylinder (840i) -The 335 bhp B58 is widely regarded as BMW's most reliable modern six-cylinder. Delivering 500 Nm of torque and 0-62 in approximately 5.2 seconds, it offers genuine grand touring performance with proven durability. The TU2 version (2020+) adds mild improvements without compromising reliability.

“”

Who it's for: buyers who want the sweet spot of performance, refinement, and reliability.

Best Diesel Overall

B57D30B 3.0-litre six-cylinder (840d xDrive) -The 315–340 bhp B57 six-cylinder diesel delivers effortless torque (680–700 Nm), excellent refinement, and genuine durability for high-mileage grand touring. The mild-hybrid system adds efficiency without complexity.

“”

Who it's for: high-mileage buyers who want effortless torque and 40+ mpg economy.

Highest Risk

N63B44D/N63B44T3 4.4-litre V8 (M850i xDrive) -The hot-vee V8 design places turbochargers in the engine's 'V', generating significant heat. Valve stem seal wear and cooling system leaks are well-documented on N63-family engines. The updated TU3 version (2020+) is improved but still demands meticulous maintenance.

“”

Who it's for: buyers who accept the premium and keep the car under warranty.

Most Expensive Failure

S63B44B/S63B44T4 4.4-litre V8 (M8 Competition) -The 625 bhp S63 is the most expensive powertrain in the G14 line-up to replace, with reconditioned units costing £8,000–£14,000. The high-performance V8 shares the N63's hot-vee architecture with additional stresses from higher boost and output.

“”

Who it's for: collectors and enthusiasts who accept the premium.

Best Value

B58B30M1 3.0-litre six-cylinder (840i) -The 335 bhp B58 offers the best balance of performance, refinement, and running costs. It's the most common G14 engine, parts are widely available, and the recon cost is significantly lower than the V8 options.

“”

Who it's for: the majority of G14 buyers who want genuine grand touring performance without V8 running costs.

Most Overlooked

B57D30B 3.0-litre diesel (840d xDrive) -Often overlooked by buyers who default to the petrol six or V8, the 840d delivers effortless torque, 40+ mpg economy, and genuine long-distance capability. With 680 Nm of torque and 0-62 in approximately 5.1 seconds, it's the ultimate motorway cruiser in the G14 range.

“”

Who it's for: buyers who prioritise long-distance touring economy without sacrificing performance.

BMW 8 Series G14 -Ownership Economics

EngineTypical MileageCommon Major FailureRepair Cost (Specialist)Replacement Cost (Recon)Ownership Verdict

B58B30C/M1 (840i)40k–80kHPFP, cooling system£800–£1,500£4,800–£8,000

Best Petrol -reliable six-cylinder

N63B44D/T3 (M850i)30k–60kValve stem seals, cooling£3,000–£6,000£6,000–£10,000

Highest Risk -V8 ownership is expensive

S63B44B/T4 (M8 Comp)20k–50kValve stem seals, cooling, turbo£4,000–£8,000£8,000–£14,000

Premium Choice -M car running costs

B57D30B (840d)60k–120kDPF blockage, EGR valve£500–£1,500£4,500–£7,500

Best Diesel -effortless torque

EngineTypical MileageCommon Major FailureRepair Cost (Specialist)Replacement Cost (Recon)Ownership Verdict

B58B30C/M1 (840i)40k–80kHPFP, cooling system£800–£1,500£4,800–£8,000

Best Petrol -reliable six-cylinder

N63B44D/T3 (M850i)30k–60kValve stem seals, cooling£3,000–£6,000£6,000–£10,000

Highest Risk -V8 ownership is expensive

S63B44B/T4 (M8 Comp)20k–50kValve stem seals, cooling, turbo£4,000–£8,000£8,000–£14,000

Premium Choice -M car running costs

B57D30B (840d)60k–120kDPF blockage, EGR valve£500–£1,500£4,500–£7,500

Best Diesel -effortless torque

The G14 rule

A £6,000–£10,000 N63 recon against a £30,000–£40,000 early G14 sits at 15–33% of the car's value -safe. Against a well-kept £50,000+ example, the same recon drops to a routine 12–20% -a repair decision, not a financial one. For a high-value luxury car, the 70% BMW threshold rarely applies, but we'll still honestly tell you when a repair doesn't make sense.

Key Takeaways

Which G14 Costs Least To Own?
B57 840d -best economy, lowest recon cost.
Which G14 Costs Most To Own?
S63 M8 Competition -valve stem seals and turbo repairs are expensive.
Which G14 Is Best Value?
B58 840i -the sweet spot between performance and running costs.

Common Problems

01

N63/S63

V8 Valve Stem Seal Wear

Affected models:

G14 M850i xDrive (N63B44D/N63B44T3) and M8 Competition (S63B44B/S63B44T4).

Typical failure mileage:

30,000–60,000 miles.

Root cause:

The hot-vee V8 design generates significant heat, causing valve stem seals to harden and wear prematurely. Blue smoke on startup is the classic warning sign; ignored, it leads to oil consumption and potential catalytic converter damage.

Tiered Cost Table

Preventative (Repair)

Dealer

Specialist

£4,000–£6,000

£3,000–£5,000

Valve stem seal replacement

Catastrophic (Replacement)

Dealer

Specialist

£8,000–£12,000

£6,000–£10,000

Full reconditioned engine

Our Recommendation

On any M850i or M8, watch for blue smoke on startup -a £3,000–£5,000 preventative repair is cheaper than the £6,000–£10,000+ replacement that follows if ignored.

Compare N63/S63 engine prices for your G14

02

B58

High-Pressure Fuel Pump (HPFP) Failure

Affected models:

G14 840i (B58B30C/B58B30M1), all years.

B58 High-Pressure Fuel Pump (HPFP) Failure

Typical failure mileage:

40,000–80,000 miles.

Root cause:

The high-pressure fuel pump on B58 engines can fail, leading to long cranking times before the engine starts, noticeable loss of power, engine misfires, and even stalling. The issue can be intermittent, making diagnosis challenging.

Tiered Cost Table

Preventative (Repair)

Dealer

Specialist

£1,200–£2,000

£800–£1,500

HPFP replacement, fuel system flush

Catastrophic (Replacement)

Dealer

Specialist

£5,500–£9,000

£4,800–£8,000

Full reconditioned engine

Our Recommendation

If your G14 840i exhibits long cranking or power loss, have the HPFP inspected immediately -an £800–£1,500 preventative repair is cheaper than the £4,800–£8,000 replacement that follows if ignored.

Compare B58 engine prices for your G14

03

B57

Diesel DPF & EGR Issues

Affected models:

G14 840d xDrive (B57D30B).

Typical failure mileage:

60,000–120,000 miles.

Root cause:

DPF blockage is common on cars used predominantly for urban driving, with fault codes indicating DPF sensor failure. EGR cooler issues can also develop. The mild-hybrid system adds some complexity to the diesel powertrain.

Tiered Cost Table

Preventative (Repair)

Dealer

Specialist

£800–£1,500

£500–£1,200

EGR cooler replacement, DPF regeneration

Catastrophic (Replacement)

Dealer

Specialist

£4,000–£6,000

£2,800–£5,000

Full reconditioned engine

Our Recommendation

On any G14 diesel, ensure regular motorway runs for DPF regeneration -a £500–£1,200 preventative service is cheaper than the £2,800–£5,000 replacement that follows if ignored.

Compare B57 engine prices for your G14

G14 Powertrain Replacement Costs -By Variant and Condition

VariantEngine CodeUsed (Supply)Reconditioned (Supply)Rebuilt (Supply)Labour Hours

840i/840i xDriveB58B30C/M1£2,500–£4,500£4,800–£8,000£6,500–£10,00012–16 hrs

M850i xDriveN63B44D/T3£3,500–£6,000£6,000–£10,000£8,000–£14,00016–22 hrs

M8 CompetitionS63B44B/T4£5,000–£8,000£8,000–£14,000£12,000–£18,00018–24 hrs

840d xDriveB57D30B£2,500–£4,500£4,500–£7,500£6,000–£9,50012–16 hrs

Core Variants

Diesel & Petrol Lineup

Diesel Variants

840d xDrive

Petrol Variants

840i840i xDriveM850i xDriveM8 Competition

Scope note: All variants listed are G14 8 Series Convertible only. The G15 Coupé and G16 Gran Coupé share these powertrains but are covered on their own Generation Pages. The M8 Competition is the high-performance variant powered by the S63 V8. The LCI facelift (2020) introduced the updated B58B30M1 and N63B44T3 engines, along with mild-hybrid technology on the 840d.

Diesel & Petrol Lineup

Diesel Variants

840d xDrive

Petrol Variants

840i840i xDriveM850i xDriveM8 Competition

Scope note: All variants listed are G14 8 Series Convertible only. The G15 Coupé and G16 Gran Coupé share these powertrains but are covered on their own Generation Pages. The M8 Competition is the high-performance variant powered by the S63 V8. The LCI facelift (2020) introduced the updated B58B30M1 and N63B44T3 engines, along with mild-hybrid technology on the 840d.

Market Intelligence

Most Requested E90 Engines (2025)

Most Requested E90 Variants

1.1. 840i (3.0 petrol)
2.2. M850i xDrive (4.4 V8)
3.3. M8 Competition (4.4 V8 high-output)

Average E90 Replacement Cost

£4,500–£14,000 supply-only [BMW-QUOTE]

Most Common E90 Failures

1.1. N63/S63 V8 valve stem seal wear
2.2. B58 HPFP failure
3.3. B57 diesel DPF & EGR issues

Live Feed

VehicleLocationIssueEnquiries

BMW 8 Series 840i

G14 (B58)

London

Long cranking on startup

4

enquiries

BMW 8 Series M850i

G14 (N63)

Birmingham

Blue smoke on startup

3

enquiries

BMW 8 Series M8 Competition

G14 (S63)

Manchester

Oil consumption, valve stem seals

2

enquiries

Updated Monthly

FAQ

BMW 3 Series E90 rear three-quarter view

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covering every variant from 840i to M8 Competition, with supply-only or full supply & fit available nationwide.

Find the best BMW 8 Series G14 powertrain replacement UK drivers rely on. Compare real prices from trusted specialists on EnginesMarket today and get back on the road with confidence.

Compare BMW 8 Series G14 Powertrain Prices on EnginesMarket

Why UK BMW 8 Series G14 Owners Trust bmwengines.uk

Trusted G14 Powertrain Specialists
every garage and engine rebuilder in our network is vetted, rated and reviewed by real 8 Series owners, as part of the Engine Finders network.
Compare G14 Powertrain Replacement Companies
see prices, warranty terms and supply & fit options side-by-side before you commit.
UK Powertrain Replacement Services for G14
covering every variant from 840i to M8 Competition, with supply-only or full supply & fit available nationwide.

Find the best BMW 8 Series G14 powertrain replacement UK drivers rely on. Compare real prices from trusted specialists on EnginesMarket today and get back on the road with confidence.

Compare BMW 8 Series G14 Powertrain Prices on EnginesMarket

BMW 8 Series G14 Engines -The Complete UK Guide

BMW 8 Series G14 Powertrain Codes -The Complete Database

BMW 8 Series G14 -Overview

BMW 8 Series G14 -Overview

Best &amp; Worst Engines

BMW 8 Series G14 -Ownership Economics

Common Problems

G14 Powertrain Replacement Costs -By Variant and Condition

Diesel &amp; Petrol Lineup

Diesel &amp; Petrol Lineup

Market Intelligence

FAQ

Why UK BMW 8 Series G14 Owners Trust bmwengines.uk

Why UK BMW 8 Series G14 Owners Trust bmwengines.uk

Best & Worst Engines

Diesel & Petrol Lineup

Diesel & Petrol Lineup