BMW 8 Series E31Coupé1990–1999
Every engine fitted to the E31 8 Series — from the 4.0-litre M60 V8 to the 5.6-litre S70 V12 that powered the 850CSi.
Real UK costs and honest reliability data for BMW's flagship V8 and V12 grand tourer.
Backed by 120+ real UK E31 enquiries in 2025 [BMW-VERIFIED].
Engine Database
Every engine fitted to the E31 8 Series — spanning the M60 and M62 V8s, and the M70, M73 and S70 V12s that defined BMW's flagship grand tourer.
Overview
The E31 is the first generation of the BMW 8 Series, unveiled at the 1989 Frankfurt Motor Show. Production began in February 1990 and continued until May 1999. Designed as BMW's flagship grand tourer, the E31 was powered by a range of naturally aspirated V8 and V12 engines — a deliberate move away from the inline-six engines that had powered BMW's coupes for decades.
The range initially launched with the M70-powered 850i V12, followed by the V8-powered 840Ci in 1993. A significant mid-life update brought the M73 5.4-litre V12 and M62 4.4-litre V8, while the S70-powered 850CSi remained the range-topping performance variant until production ended in 1996.
Key Facts
Market Intelligence
The E31 8 Series generated 120+ real UK engine enquiries in 2025 [BMW-VERIFIED], concentrated on the V8 840Ci and V12 850Ci as classic car buyers seek BMW's flagship grand tourer.
04Best & Worst Engines
Highest Risk
M70B50 (850i, 5.0L V12, 296 bhp)
“The M70 is a robust, over-engineered unit but age has taken its toll — distributor cap and rotor issues, fuel system problems, and cooling system failures are common on 30+ year-old examples. The early engine management system is less sophisticated than the M73's.”
Who it's for: buyers on a budget who are willing to invest in maintenance.
Most Expensive Failure
S70B56 (850CSi, 5.6L V12, 375–380 bhp)
“The S70 is the most expensive engine to maintain and replace in the E31 range — specialist parts are scarce, and a full rebuild can exceed £14,000. The 850CSi is a future classic, but it comes with six-figure maintenance expectations.”
Who it's for: collectors with deep pockets and specialist support.
Best Value
M60B40 (840Ci, 4.0L V8, 282 bhp)
“The M60-powered 840Ci is the most affordable entry point to E31 ownership — V8 running costs are significantly lower than the V12s, and the M60 is a proven engine (though check for Nikasil lining issues on early cars). It offers 90% of the 850i experience at a fraction of the price.”
Who it's for: buyers who want E31 ownership without V12 running costs.
Most Overlooked
M73B54 (850Ci, 5.4L V12, 322 bhp)
“The M73 is often overshadowed by the S70 — but it's the smart V12 buy. More power than the M70 (322 bhp vs 296), better engine management (Siemens OBD II), and significantly more reliable than its predecessor. It's the V12 to buy if you can't stretch to an 850CSi.”
Who it's for: buyers who want V12 refinement with modern(ish) engine management.
Highest Risk
M70B50
(850i, 5.0L V12, 296 bhp)
“The M70 is a robust, over-engineered unit but age has taken its toll — distributor cap and rotor issues, fuel system problems, and cooling system failures are common on 30+ year-old examples. The early engine management system is less sophisticated than the M73's.”
Who it's for: buyers on a budget who are willing to invest in maintenance.
Most Expensive Failure
S70B56
(850CSi, 5.6L V12, 375–380 bhp)
“The S70 is the most expensive engine to maintain and replace in the E31 range — specialist parts are scarce, and a full rebuild can exceed £14,000. The 850CSi is a future classic, but it comes with six-figure maintenance expectations.”
Who it's for: collectors with deep pockets and specialist support.
Best Value
M60B40
(840Ci, 4.0L V8, 282 bhp)
“The M60-powered 840Ci is the most affordable entry point to E31 ownership — V8 running costs are significantly lower than the V12s, and the M60 is a proven engine (though check for Nikasil lining issues on early cars). It offers 90% of the 850i experience at a fraction of the price.”
Who it's for: buyers who want E31 ownership without V12 running costs.
Most Overlooked
M73B54 (850Ci, 5.4L V12, 322 bhp)
“The M73 is often overshadowed by the S70 — but it's the smart V12 buy. More power than the M70 (322 bhp vs 296), better engine management (Siemens OBD II), and significantly more reliable than its predecessor. It's the V12 to buy if you can't stretch to an 850CSi.”
Who it's for: buyers who want V12 refinement with modern(ish) engine management.
Engine
Typical Mileage
Common Major Failure
Repair Cost (Specialist)
Replacement Cost (Recon)
Ownership Verdict
Solid Choice -check Nikasil history.
Best V8 -improved over M60.High Maintenance -over-engineered but ageing.Best V12 -more reliable than M70.Ultimate V12 -collectable, costly to maintain.EngineTypical MileageCommon Major FailureRepair Cost (Specialist)Replacement Cost (Recon)Ownership VerdictSolid Choice -check Nikasil history.Best V8 -improved over M60.High Maintenance -over-engineered but ageing.Best V12 -more reliable than M70.Ultimate V12 -collectable, costly to maintain.
The E31 rule
A £5,000–£8,000 M70 recon against a £8,000–£25,000 E31 sits at 20–100% of the car's value【BMW-QUOTE】. On a sub-£12,000 example, that brushes our 70% BMW threshold -we'll honestly tell you to walk away. Against a well-kept £20,000+ example, the same recon drops to 25–40% -a repair decision, not a financial one. Value the car first. For 850CSi cars (£30,000–£60,000+), even the most expensive S70 replacement is viable given collector values.
Key Takeaways
Which E31 Costs Least To Own?
M60/M62 840Ci -V8 running costs are significantly lower than the V12s.
Which E31 Costs Most To Own?
S70 850CSi -parts scarcity and V12 complexity make this the most expensive E31 to maintain.
Which E31 Is Best Value?
M73 850Ci (post-1994) -V12 refinement with more reliable engine management than the M70.
M60
V8 Nikasil Cylinder Lining Wear
Affected models:
E31 840Ci (1993–1995, M60B40 engine).
Typical failure mileage:
60,000–100,000 miles.
Root cause:
Early M60 V8s used Nikasil (nickel-silicon carbide) cylinder linings which could degrade when exposed to high-sulphur fuels. This led to loss of compression, increased oil consumption, and eventual engine failure. BMW issued a recall and replaced affected engines with Alusil-lined units.
Tiered Cost Table
Preventative (Repair)
Dealer
Specialist
£2,000–£4,000 (compression test + cylinder inspection)
£1,000–£2,000 (compression test + cylinder inspection)
Cylinder compression test, borescope inspection
Catastrophic (Replacement)
Dealer
Specialist
£6,000–£9,000
£4,500–£7,500
Full M60 engine replacement or rebuild
Our Recommendation
If you're buying an M60-powered 840Ci (1993–1995), get a compression test and borescope inspection before committing -£1,000–£2,000 now is far cheaper than the £4,500+ engine replacement that follows if the Nikasil linings have failed. Check the vehicle's service history for evidence of recall work.
M70
V12 Distributor Cap & Rotor Failure
Affected models:
E31 850i (1990–1994, M70B50 engine).
Typical failure mileage:
40,000–80,000 miles (age-related).
Root cause:
The M70 V12 uses two distributor caps and rotors -one for each bank of cylinders. These components degrade with age and heat, leading to misfires, rough running, and reduced performance. The caps and rotors are becoming increasingly difficult to source.
Tiered Cost Table
Preventative (Repair)
Dealer
Specialist
£800–£1,500
£500–£1,000
Distributor cap and rotor replacement
Catastrophic (Replacement)
Dealer
Specialist
£5,000–£8,000
£4,500–£7,000
Full M70 engine replacement if misfire caused damage
Our Recommendation
Replace the distributor caps and rotors every 40,000 miles or 5 years -a £500–£1,000 specialist job is cheap insurance against a £4,500+ engine replacement that follows if misfire damage occurs. Keep a spare set if you plan to keep the car long-term -these parts are getting harder to find.
E31
Cooling System Failure (All Engines)
Affected models:
All E31 models (M60, M62, M70, M73, S70).
Typical failure mileage:
50,000–100,000 miles.
Root cause:
The E31's cooling system uses plastic components that become brittle with age -water pumps, radiators, expansion tanks and hoses are all potential failure points. Overheating can cause catastrophic engine damage on both V8 and V12 engines.
Tiered Cost Table
Preventative (Repair)
Dealer
Specialist
£1,000–£2,000
£600–£1,500
Water pump, thermostat, radiator, hoses replacement
Catastrophic (Replacement)
Dealer
Specialist
£5,000–£9,000
£4,500–£8,000
Full engine replacement if overheating caused damage
Our Recommendation
Replace the entire cooling system (water pump, thermostat, radiator, expansion tank, hoses) as preventative maintenance at 60,000 miles or 10 years -a £600–£1,500 specialist job is dramatically cheaper than the £4,500+ engine replacement that follows an overheating event. This is the single most important maintenance item on any E31.
E31
Fuel System & Injector Issues (All Engines)
Affected models:
All E31 models, particularly V12s (M70, M73, S70).
Typical failure mileage:
50,000–100,000 miles (age-related).
Root cause:
The E31's fuel system is complex -the V12s have two separate fuel rails and two fuel pumps. Fuel injectors can become clogged or fail with age, leading to rough running, poor economy, and potential engine damage. The fuel pumps are also a known weak point.
Tiered Cost Table
Preventative (Repair)
Dealer
Specialist
£1,000–£2,000
£500–£1,500
Fuel injector cleaning/replacement, fuel pump replacement
Catastrophic (Replacement)
Dealer
Specialist
£5,000–£9,000
£4,500–£8,000
Full engine replacement if fuel starvation caused damage
Our Recommendation
Have the fuel injectors cleaned or replaced at 60,000 miles -a £500–£1,500 specialist job is far cheaper than the £4,500+ engine replacement that follows if fuel starvation causes a lean-running failure. On V12 cars, budget for two fuel pumps if they haven't been replaced.
VariantEngine Code
Used (Supply)
Reconditioned (Supply)
Rebuilt (Supply)
Labour HoursNo Generation variance from the EM_Proprietary_Data baseline figures -E31 is a unique generation with no direct successor cost comparison. Costs are derived from specialist market data and tagged [BMW-QUOTE].
Petrol Variants
Scope note: All variants listed are E31 8 Series only. The 840Ci switched from the M60B40 (1993–1995) to the M62B44 (1995–1999). The 850i (1990–1994) used the M70B50; the 850Ci (1994–1999) used the M73B54. The 850CSi (1992–1996) used the S70B56 and was the only E31 offered exclusively with a 6-speed manual transmission. The 850i became the 850Ci around the introduction of the 850CSi -both M70 and M73-engined cars were sold as 850Ci for a period in 1994.
Most Requested Engines (2025)
Most Requested Variants
Average Replacement Cost
£5,500
reconditioned, supply only
[BMW-QUOTE]
Most Common Failures
Live FeedBMW 8 Series
E31 840Ci
London
Cooling system inspection3
enquiries
Updated MonthlyBMW 8 Series
E31 850Ci
SurreyPre-purchase inspection2
enquiries
Updated MonthlyBMW 8 Series
E31 850CSi
OxfordRod bearing inspection1
enquiry
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
Petrol Variants
Scope note: All variants listed are E31 8 Series only. The 840Ci switched from the M60B40 (1993–1995) to the M62B44 (1995–1999). The 850i (1990–1994) used the M70B50; the 850Ci (1994–1999) used the M73B54. The 850CSi (1992–1996) used the S70B56 and was the only E31 offered exclusively with a 6-speed manual transmission. The 850i became the 850Ci around the introduction of the 850CSi -both M70 and M73-engined cars were sold as 850Ci for a period in 1994.
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 8 Series
E31 840Ci
LondonCooling system inspection3
enquiries
BMW 8 Series
E31 850Ci
SurreyPre-purchase inspection2
enquiries
BMW 8 Series
E31 850CSi
OxfordRod bearing inspection1
enquiry
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