BMW 8 Series G16Gran Coupé2019–present
Every engine fitted to the G16 Gran Coupé — from the 3.0‑litre B58 six‑cylinder in the 840i to the 4.4‑litre N63 V8 in the M850i xDrive, plus the S63‑powered M8 and the B57 diesel.
Real UK replacement costs, honest reliability data, and the hot‑vee cooling system quirks that define this generation.
Backed by real UK G16 enquiries in 2025 [BMW-VERIFIED].
Engine Database
Every engine fitted to the G16 Gran Coupé — from the entry‑level six‑cylinder petrol to the range‑topping M8.
Overview
The BMW G16, announced in June 2019 and launched from September 2019, is the four‑door Gran Coupé version of the second‑generation 8 Series. It sits on the BMW CLAR platform shared with the G15 coupé and G14 convertible, but with a wheelbase extended by 201 mm (7.9 in) for improved rear passenger space.
The G16 is the only model in its segment derived directly from a two‑door sports car, featuring a body structure built with aluminium, magnesium and carbon fibre‑reinforced plastic for low weight and high rigidity.
Key Facts
Market Intelligence
The G16 generated real UK engine enquiries in 2025 [BMW-VERIFIED], with the B58 six‑cylinder and N63 V8 accounting for the majority of demand as these luxury grand tourers enter their second ownership cycles.
04Best & Worst Engines
Best Diesel Overall
B57D30 (840d xDrive) – "The 3.0‑litre straight‑six diesel delivers 340 PS with effortless torque and a smooth, refined character that suits the Gran Coupé's grand touring mission. The 8 kW mild‑hybrid boost smooths stop‑start and aids off‑line response. No timing chain anxiety here – the B57 is a proven, robust unit."
“”
Who it's for: buyers who want effortless torque, long‑distance comfort and diesel economy.
Best Petrol Overall
B58B30M1 (840i) – "The B58 straight‑six is BMW's finest modern petrol engine – 340 PS of silky‑smooth power with proven reliability and a sonorous exhaust note. No V8 complexity, no hot‑vee cooling concerns – just a beautifully engineered six‑cylinder that rewards every mile. It's the sweet spot of the G16 range."
“”
Who it's for: buyers who want straight‑six refinement without the V8's running costs.
Highest Risk
N63B44T3 (M850i xDrive) – "The hot‑vee V8 design generates significant heat – cooling system components, valve stem seals and PCV systems are all under stress. While the TU3 ('Technical Update 3') version is improved over earlier N63 engines, it still demands more diligent maintenance than the B58. Budget for cooling system refreshes."
“”
Who it's for: buyers who accept V8 maintenance costs for the performance and exhaust note.
Most Expensive Failure
S63B44T4 (M8) – "The high‑output V8 is a masterpiece of engineering, but any internal failure – turbocharger, timing chain or valvetrain – can run to £14,000+. This is not an engine for the faint‑hearted, and parts are expensive and specialist‑only."
“”
Who it's for: buyers with deep pockets and full service history who want M‑division performance.
Best Value
B58B30M1 (840i) – "The entry‑level six‑cylinder delivers 340 PS – more than enough for the Gran Coupé's grand touring mission – with significantly lower running costs than the V8s. No complex hot‑vee cooling system, better fuel economy, and lower insurance. It's the smart choice."
“”
Who it's for: buyers who want G16 presence and six‑cylinder refinement without the V8 premium.
Most Overlooked
B57D30 (840d xDrive) – "The diesel six is often overlooked by UK buyers who default to petrol, but it delivers 340 PS with 700 N·m of torque – more than the B58 petrol. Effortless, refined and surprisingly economical for a car of this size. Most buyers don't consider it, but they should."
“”
Who it's for: buyers who cover high mileage and want effortless torque.
Best Diesel Overall
B57D30
(840d xDrive) – "The 3.0‑litre straight‑six diesel delivers 340 PS with effortless torque and a smooth, refined character that suits the Gran Coupé's grand touring mission. The 8 kW mild‑hybrid boost smooths stop‑start and aids off‑line response. No timing chain anxiety here – the B57 is a proven, robust unit."
“”
Who it's for: buyers who want effortless torque, long‑distance comfort and diesel economy.
Best Petrol Overall
B58B30M1
(840i) – "The B58 straight‑six is BMW's finest modern petrol engine – 340 PS of silky‑smooth power with proven reliability and a sonorous exhaust note. No V8 complexity, no hot‑vee cooling concerns – just a beautifully engineered six‑cylinder that rewards every mile. It's the sweet spot of the G16 range."
“”
Who it's for: buyers who want straight‑six refinement without the V8's running costs.
Highest Risk
N63B44T3
(M850i xDrive) – "The hot‑vee V8 design generates significant heat – cooling system components, valve stem seals and PCV systems are all under stress. While the TU3 ('Technical Update 3') version is improved over earlier N63 engines, it still demands more diligent maintenance than the B58. Budget for cooling system refreshes."
“”
Who it's for: buyers who accept V8 maintenance costs for the performance and exhaust note.
Most Expensive Failure
S63B44T4
(M8) – "The high‑output V8 is a masterpiece of engineering, but any internal failure – turbocharger, timing chain or valvetrain – can run to £14,000+. This is not an engine for the faint‑hearted, and parts are expensive and specialist‑only."
“”
Who it's for: buyers with deep pockets and full service history who want M‑division performance.
Best Value
B58B30M1
(840i) – "The entry‑level six‑cylinder delivers 340 PS – more than enough for the Gran Coupé's grand touring mission – with significantly lower running costs than the V8s. No complex hot‑vee cooling system, better fuel economy, and lower insurance. It's the smart choice."
“”
Who it's for: buyers who want G16 presence and six‑cylinder refinement without the V8 premium.
Most Overlooked
B57D30 (840d xDrive) – "The diesel six is often overlooked by UK buyers who default to petrol, but it delivers 340 PS with 700 N·m of torque – more than the B58 petrol. Effortless, refined and surprisingly economical for a car of this size. Most buyers don't consider it, but they should."
“”
Who it's for: buyers who cover high mileage and want effortless torque.
Engine
Typical Mileage
Common Major Failure
Repair Cost (Specialist)
Replacement Cost (Recon)
Ownership Verdict
Best Petrol – proven six, reliable and refined.
Watch – hot‑vee V8; diligent maintenance required.Expensive – high‑performance V8; specialist‑only.Best Diesel – proven six, torque‑rich and refined.Specialist – high‑output V8; Alpina‑specific parts.EngineTypical MileageCommon Major FailureRepair Cost (Specialist)Replacement Cost (Recon)Ownership VerdictBest Petrol – proven six, reliable and refined.Watch – hot‑vee V8; diligent maintenance required.Expensive – high‑performance V8; specialist‑only.Best Diesel – proven six, torque‑rich and refined.Specialist – high‑output V8; Alpina‑specific parts.
The G16 rule
A £3,500–£6,000 B58 recon against a £25,000–£40,000 G16 840i sits at 9–24% of the car's value – a routine repair decision, not a financial disaster. Even the most expensive M8 replacement at £15,000 is under 20% of a typical £80,000+ example. The BMW 70% threshold is rarely triggered on the G16 – values are high enough to absorb even significant engine bills. That said, always factor in the car's condition and service history; a neglected example may not be worth the investment.
Key Takeaways
Which G16 Costs Least To Own?
840i (B58) – cheapest entry, lower insurance, proven six‑cylinder reliability.
Which G16 Costs Most To Own?
M8 (S63) – high‑output V8 with premium running costs and specialist maintenance.
Which G16 Is Best Value?
840i (B58) – the sweet spot between performance, refinement and running costs.
B58
Water Pump & Cooling System Wear
Affected models:
G16 840i, 840i xDrive (B58B30M1).
Typical failure mileage:
60,000–100,000 miles.
Root cause:
The plastic water pump impeller and thermostat housing can degrade with heat cycling – a known characteristic of BMW's B‑series engines. Coolant leaks are the first sign, followed by overheating if ignored.
Tiered Cost Table
Preventative (Repair)
Dealer
Specialist
£800–£1,500
£400–£800
Catastrophic (Replacement)
Dealer
Specialist
£5,000–£8,000
£3,500–£6,000
Our Recommendation
At the first sign of coolant loss, have the water pump and thermostat housing inspected – a £400–£800 repair is cheap insurance against a £3,500+ replacement. Replace the coolant at the same time.
N63
V8 Cooling System & Valve Stem Seals (M850i xDrive)
Affected models:
G16 M850i xDrive (N63B44T3).
Typical failure mileage:
40,000–80,000 miles.
Root cause:
The hot‑vee V8 design generates significant heat – valve stem seals can harden and leak, causing oil consumption and blue smoke on startup. Coolant hoses and plastic fittings near the turbochargers also degrade. While the TU3 version is improved over earlier N63 engines, these issues remain.
Tiered Cost Table
Preventative (Repair)
Dealer
Specialist
£2,500–£4,000
£1,000–£2,500
Catastrophic (Replacement)
Dealer
Specialist
£10,000–£15,000
£6,000–£10,000
Our Recommendation
If you own an M850i, monitor oil consumption carefully and have the cooling system inspected annually. A £1,000–£2,500 valve stem seal replacement is far cheaper than the £6,000+ replacement that follows a catastrophic failure. Use the correct BMW coolant and change it every two years.
S63
V8 Turbocharger & Timing Chain Wear (M8)
Affected models:
G16 M8, M8 Competition (S63B44T4).
Typical failure mileage:
30,000–60,000 miles.
Root cause:
The high‑output S63 V8 runs higher boost and internal stresses – the turbocharger oil feed lines can coke, and the timing chain tensioner can wear prematurely. Both can lead to catastrophic failure if ignored.
Tiered Cost Table
Preventative (Repair)
Dealer
Specialist
£3,000–£5,000
£1,500–£4,000
Catastrophic (Replacement)
Dealer
Specialist
£15,000–£20,000
£8,000–£15,000
Our Recommendation
If you own an M8, budget for a full inspection at 50,000 miles – £1,500–£4,000 now is far cheaper than the £8,000+ replacement that follows a failure. Only buy an M8 with full documented service history and evidence of regular oil changes (every 6,000 miles).
B57
EGR Cooler & AdBlue System (840d xDrive)
Affected models:
G16 840d xDrive (B57D30).
Typical failure mileage:
60,000–100,000 miles.
Root cause:
The EGR cooler can develop internal coolant leaks, and the AdBlue system can suffer from crystallisation and sensor failures – common issues across BMW's modern diesel range.
Tiered Cost Table
Preventative (Repair)
Dealer
Specialist
£800–£1,500
£400–£1,000
Catastrophic (Replacement)
Dealer
Specialist
£6,000–£9,000
£4,500–£7,500
Our Recommendation
Check if your 840d is covered by any EGR cooler recall – if not, have the cooler inspected at every service. A £400–£1,000 repair is far cheaper than the £4,500+ replacement that follows an overheat.
VariantEngine Code
Used (Supply)
Reconditioned (Supply)
Rebuilt (Supply)
Labour Hours
Diesel Variants
Petrol Variants
Scope note: All variants listed are G16 only. The G14 convertible and G15 coupé share most of these engines but are covered on their own Generation Pages. The Alpina B8 is a related variant built on the G16 platform, while the M8 is the high‑performance variant.
Most Requested Engines (2025)
Most Requested Variants
Average Replacement Cost
£3,500–£15,000 supply only .
[BMW-QUOTE]
Most Common Failures
Live FeedBMW 840i G16
B58B30M1
Birmingham
Coolant loss4
enquiries
Updated MonthlyBMW M850i xDrive G16
N63B44T3
LondonOil consumption3
enquiries
Updated MonthlyBMW M8 G16
S63B44T4
ManchesterTurbocharger inspection2
enquiries
Updated MonthlyMost Requested Engines (2025)
Most Requested Variants
Average Replacement Cost
£3,500–£15,000 supply only .
[BMW-QUOTE]
Most Common Failures
Most Requested Engines (2025)
Most Requested Variants
Average Replacement Cost
£3,500–£15,000 supply only .
[BMW-QUOTE]
Most Common Failures
Diesel Variants
Petrol Variants
Scope note: All variants listed are G16 only. The G14 convertible and G15 coupé share most of these engines but are covered on their own Generation Pages. The Alpina B8 is a related variant built on the G16 platform, while the M8 is the high‑performance variant.
Most Requested Engines (2025)
Most Requested Variants
Average Replacement Cost
£3,500–£15,000 supply only .
[BMW-QUOTE]
Most Common Failures
Most Requested Engines (2025)
Most Requested Variants
Average Replacement Cost
£3,500–£15,000 supply only .
[BMW-QUOTE]
Most Common Failures
Most Requested Engines (2025)
Most Requested Variants
Average Replacement Cost
£3,500–£15,000 supply only .
[BMW-QUOTE]
Most Common Failures
Live FeedBMW 840i G16
B58B30M1
BirminghamCoolant loss4
enquiries
BMW M850i xDrive G16
N63B44T3
LondonOil consumption3
enquiries
BMW M8 G16
S63B44T4
ManchesterTurbocharger inspection2
enquiries
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