BMW 6 Series F12Convertible2011–2018
Every engine fitted to the F12 Convertible — from the 3.0-litre N55 straight-six to the 4.4-litre twin-turbo V8 and the S63-powered M6.
Real UK costs and honest reliability data for BMW's luxurious grand tourer convertible.
Backed by 120+ real UK F12 enquiries in 2025 [BMW-VERIFIED].
Engine Database
Every engine fitted to the F12 Convertible specifically — spanning the N55 straight-six petrol, the N57 straight-six diesel, the N63 V8 petrol, the S63 V8 in the M6, and their LCI updates.
Overview
The F12 is the convertible body of BMW's third-generation 6 Series, unveiled at the 2011 Shanghai Auto Show. It shares the L6 platform with the F10 5 Series and F01 7 Series, offering a luxurious grand tourer experience with a fabric roof that operates at speeds up to 40 km/h. The engine line-up featured a 3.0-litre straight-six petrol (640i), a 3.0-litre straight-six diesel (640d), a 4.4-litre V8 petrol (650i), and the S63 V8-powered M6.
A late 2014 LCI facelift brought an output boost for the 650i to 450 PS and subtle styling updates. The F12 was produced until September 2018, succeeded by the G14 8 Series Convertible.
Key Facts
Market Intelligence
The F12 Convertible generated 120+ real UK engine enquiries in 2025 [BMW-VERIFIED], concentrated on the 640i petrol and 640d diesel as the range reaches affordable used-car territory.
04Best & Worst Engines
Best Petrol Overall
N55B30A (640i, 3.0L straight-six, 320 PS)
“BMW's N55 single-turbo straight-six is a proven, reliable engine — smooth, responsive, and with a strong torque curve from 1,300 rpm. The 640i offers effortless grand touring performance without the V8's running costs.”
Who it's for: buyers who want six-cylinder refinement with sensible running costs.
Best Diesel Overall
N57D30B (640d, 3.0L straight-six diesel, 313 PS)
“The N57 straight-six diesel is a masterpiece of refinement and efficiency — 313 PS, 630 Nm of torque, and genuine 40+ mpg capability. The 640d offers the best blend of performance and economy in the F12 range.”
Who it's for: buyers who want effortless torque and long-distance cruising capability.
Highest Risk
N63B44A/B (650i, 4.4L V8, 407–450 PS)
“The N63 'hot-vee' V8 is a spectacular engine but has a reputation for heat-related failures — valve stem seal wear is the most common issue, leading to blue smoke on startup. The LCI's N63B44B is improved but still requires careful maintenance.”
Who it's for: 650i buyers with deep pockets and full service history.
Most Expensive Failure
S63B44B (M6 Convertible, 4.4L V8, 560 PS)
“The S63 V8 in the M6 is the most powerful and most expensive engine in the F12 range — rod bearing wear is a known issue on early examples, and a full replacement can exceed £15,000. The M6 is a future classic, but it comes with M-car running costs.”
Who it's for: collectors and enthusiasts who want the ultimate F12 experience.
Best Value
N57D30B (640d, 3.0L diesel, 313 PS)
“The 640d offers near-650i performance with significantly lower running costs — 313 PS, 630 Nm of torque, and excellent fuel economy. It's the smart buy for anyone covering serious mileage in their grand tourer.”
Who it's for: buyers who want effortless performance with sensible economy.
Most Overlooked
N55B30A (640i, 3.0L petrol, 320 PS)
“The 640i is often overlooked in favour of the V8 650i or the diesel 640d — but it's the sweet spot for many buyers. The N55 is proven and reliable, the power is more than adequate, and running costs are significantly lower than the V8. It's the most balanced engine in the F12 range.”
Who it's for: buyers who want six-cylinder refinement without diesel clatter or V8 bills.
Best Petrol Overall
N55B30A
(640i, 3.0L straight-six, 320 PS)
“BMW's N55 single-turbo straight-six is a proven, reliable engine — smooth, responsive, and with a strong torque curve from 1,300 rpm. The 640i offers effortless grand touring performance without the V8's running costs.”
Who it's for: buyers who want six-cylinder refinement with sensible running costs.
Best Diesel Overall
N57D30B
(640d, 3.0L straight-six diesel, 313 PS)
“The N57 straight-six diesel is a masterpiece of refinement and efficiency — 313 PS, 630 Nm of torque, and genuine 40+ mpg capability. The 640d offers the best blend of performance and economy in the F12 range.”
Who it's for: buyers who want effortless torque and long-distance cruising capability.
Highest Risk
N63B44A/B
(650i, 4.4L V8, 407–450 PS)
“The N63 'hot-vee' V8 is a spectacular engine but has a reputation for heat-related failures — valve stem seal wear is the most common issue, leading to blue smoke on startup. The LCI's N63B44B is improved but still requires careful maintenance.”
Who it's for: 650i buyers with deep pockets and full service history.
Most Expensive Failure
S63B44B
(M6 Convertible, 4.4L V8, 560 PS)
“The S63 V8 in the M6 is the most powerful and most expensive engine in the F12 range — rod bearing wear is a known issue on early examples, and a full replacement can exceed £15,000. The M6 is a future classic, but it comes with M-car running costs.”
Who it's for: collectors and enthusiasts who want the ultimate F12 experience.
Best Value
N57D30B
(640d, 3.0L diesel, 313 PS)
“The 640d offers near-650i performance with significantly lower running costs — 313 PS, 630 Nm of torque, and excellent fuel economy. It's the smart buy for anyone covering serious mileage in their grand tourer.”
Who it's for: buyers who want effortless performance with sensible economy.
Most Overlooked
N55B30A (640i, 3.0L petrol, 320 PS)
“The 640i is often overlooked in favour of the V8 650i or the diesel 640d — but it's the sweet spot for many buyers. The N55 is proven and reliable, the power is more than adequate, and running costs are significantly lower than the V8. It's the most balanced engine in the F12 range.”
Who it's for: buyers who want six-cylinder refinement without diesel clatter or V8 bills.
Engine
Typical Mileage
Common Major Failure
Repair Cost (Specialist)
Replacement Cost (Recon)
Ownership Verdict
Solid Choice -proven N55, reliable.Best Diesel -refined and durable.
High Cost -spectacular V8, costly to maintain.Performance Icon -budget for maintenance.EngineTypical MileageCommon Major FailureRepair Cost (Specialist)Replacement Cost (Recon)Ownership VerdictSolid Choice -proven N55, reliable.Best Diesel -refined and durable.High Cost -spectacular V8, costly to maintain.Performance Icon -budget for maintenance.
The F12 rule
A £4,500–£7,500 N57 recon against a £8,000–£25,000 F12 sits at 18–94% of the car's value【EM-VERIFIED】. On a sub-£10,000 example, that brushes our 70% BMW threshold -we'll honestly tell you to walk away. Against a well-kept £15,000+ example, the same recon drops to 30–50% -a repair decision, not a financial one. Value the car first. For M6 cars (£20,000–£40,000+), even the most expensive S63 replacement is viable given collector values.
Key Takeaways
Which F12 Costs Least To Own?
N57 640d -excellent fuel economy, fewer major failure modes than the V8s.
Which F12 Costs Most To Own?
S63 M6 -rod bearings, V8 complexity and M-car running costs add up fast.
Which F12 Is Best Value?
N55 640i -proven six-cylinder reliability, strong performance, and lower running costs than the V8.
N63
V8 Valve Stem Seal Wear
Affected models:
F12 650i, 650i xDrive (2011–2018, N63 engine).
Typical failure mileage:
40,000–80,000 miles.
Root cause:
The N63 'hot-vee' design places the turbochargers inside the V of the engine, leading to heat-related valve stem seal hardening. This causes oil to leak past the seals into the combustion chamber, resulting in blue smoke on startup and increased oil consumption. BMW issued technical service bulletins for valve seal replacement.
Tiered Cost Table
Preventative (Repair)
Dealer
Specialist
£3,000–£5,000
£1,500–£3,500
Valve stem seal replacement (specialist tool required)
Catastrophic (Replacement)
Dealer
Specialist
£10,000–£14,000
£6,000–£10,000
Full reconditioned N63 engine replacement
Our Recommendation
If you're buying an N63-powered F12 650i, budget for valve stem seal replacement immediately unless there's documented proof it's already been done -£1,500–£3,500 now is far cheaper than the £6,000+ engine replacement that follows if ignored. Blue smoke on startup is the classic warning sign -don't ignore it.
S63
Rod Bearing Wear (M6)
Affected models:
F12 M6 Convertible (2012–2018, S63 engine).
Typical failure mileage:
30,000–70,000 miles.
Root cause:
Early S63 engines can suffer from rod bearing wear -a known issue shared with the S65 V8 in the E9x M3. Oil starvation and clearance issues can lead to bearing failure and catastrophic engine damage. This is the single most important maintenance item on any S63-powered BMW.
Tiered Cost Table
Preventative (Repair)
Dealer
Specialist
£3,000–£5,000
£2,000–£3,500
Rod bearing replacement with upgraded bearings
Catastrophic (Replacement)
Dealer
Specialist
£14,000–£20,000
£9,000–£15,000
Full S63 engine replacement
Our Recommendation
If you're buying an F12 M6, budget for rod bearing replacement immediately unless there's documented proof it's already been done -£2,000–£3,500 now is dramatically cheaper than the £9,000+ engine replacement that follows a bearing failure. This is not optional; it's the defining maintenance item of the S63 V8.
N55
HPFP & VANOS Issues
Affected models:
F12 640i, 640i xDrive (2011–2018, N55 engine).
Typical failure mileage:
50,000–100,000 miles.
Root cause:
The N55 can suffer from high-pressure fuel pump (HPFP) failure and VANOS solenoid issues -though less common than on the earlier N54. HPFP failure leads to long cranking and limp mode; VANOS issues cause rough running and reduced performance.
Tiered Cost Table
Preventative (Repair)
Dealer
Specialist
£1,200–£2,000
£700–£1,500
HPFP and VANOS solenoid replacement
Catastrophic (Replacement)
Dealer
Specialist
£6,000–£9,000
£4,000–£7,000
Full reconditioned N55 engine replacement
Our Recommendation
Have the HPFP and VANOS system inspected at 60,000 miles -a £700–£1,500 preventative service is far cheaper than the £4,000+ replacement that follows a catastrophic failure. If you experience long cranking on startup, investigate immediately.
N57
Diesel EGR Cooler & Emission System Issues
Affected models:
F12 640d, 640d xDrive (2011–2018, N57 engine).
Typical failure mileage:
60,000–120,000 miles.
Root cause:
The N57 diesel's EGR cooler can develop internal leaks, allowing coolant to enter the exhaust system. DPF clogging (urban driving) and AdBlue system issues (where fitted) are also common. BMW has issued recalls for EGR cooler issues on some models.
Tiered Cost Table
Preventative (Repair)
Dealer
Specialist
£800–£1,500 (recall may cover)
£500–£1,000
EGR cooler replacement, DPF clean, AdBlue system service
Catastrophic (Replacement)
Dealer
Specialist
£6,000–£9,000
£4,500–£7,500
Full engine replacement if coolant contamination caused damage
Our Recommendation
Check your N57 F12's VIN against any outstanding EGR cooler recalls -if affected, the repair is free. For DPF health, ensure regular motorway driving to allow regeneration cycles to complete. Have the emission system inspected at 60,000 miles.
VariantEngine Code
Used (Supply)
Reconditioned (Supply)
Rebuilt (Supply)
Labour HoursNo Generation variance from the EM_Proprietary_Data baseline figures -F12 Convertible shares the L6 platform with the F10 5 Series, with similar engine-bay access, so costs are inherited directly per the Authority Model, with no divergence note required.
Diesel Variants
Petrol Variants
Scope note: All variants listed are F12 Convertible only. F13 Coupé and F06 Gran Coupé share the same engine families but are covered on their own Generation Pages. The LCI (late 2014) brought the N63B44B with 450 PS for the 650i. M6 Convertible features the S63B44B V8 with 560 PS.
Most Requested Engines (2025)
Most Requested Variants
Average Replacement Cost
£5,500
reconditioned, supply only
[BMW-QUOTE]
Most Common Failures
Live FeedBMW 6 Series
F12 640i
London
HPFP inspection3
enquiries
Updated MonthlyBMW 6 Series
F12 640d
BirminghamEGR cooler recall check2
enquiries
Updated MonthlyBMW 6 Series
F12 M6
SurreyRod bearing inspection2
enquiries
Updated MonthlyMost Requested Engines (2025)
Most Requested Variants
Average Replacement Cost
£5,500
reconditioned, supply only
[BMW-QUOTE]
Most Common Failures
Most Requested Engines (2025)
Most Requested Variants
Average Replacement Cost
£5,500
reconditioned, supply only
[BMW-QUOTE]
Most Common Failures
Diesel Variants
Petrol Variants
Scope note: All variants listed are F12 Convertible only. F13 Coupé and F06 Gran Coupé share the same engine families but are covered on their own Generation Pages. The LCI (late 2014) brought the N63B44B with 450 PS for the 650i. M6 Convertible features the S63B44B V8 with 560 PS.
Most Requested Engines (2025)
Most Requested Variants
Average Replacement Cost
£5,500
reconditioned, supply only
[BMW-QUOTE]
Most Common Failures
Most Requested Engines (2025)
Most Requested Variants
Average Replacement Cost
£5,500
reconditioned, supply only
[BMW-QUOTE]
Most Common Failures
Most Requested Engines (2025)
Most Requested Variants
Average Replacement Cost
£5,500
reconditioned, supply only
[BMW-QUOTE]
Most Common Failures
Live FeedBMW 6 Series
F12 640i
LondonHPFP inspection3
enquiries
BMW 6 Series
F12 640d
BirminghamEGR cooler recall check2
enquiries
BMW 6 Series
F12 M6
SurreyRod bearing inspection2
enquiries
Updated MonthlyTrusted F12 Engine Suppliers
every garage and engine rebuilder in our network is vetted, rated and reviewed by real 6 Series Convertible owners, as part of the Engine Finders network.
Compare F12 Engine Replacement Companies
see prices, warranty terms and supply & fit options side-by-side before you commit.
UK Engine Replacement Services for F12
covering every variant from 640i to M6, with supply-only or full supply & fit available nationwide.
Find the best BMW 6 Series F12 engine replacement UK drivers rely on. Compare real prices from trusted specialists on EnginesMarket today and get back on the road with confidence.
Compare BMW 6 Series F12 Engine Prices on EnginesMarket