How much does a BMW M20 engine replacement cost?

A reconditioned M20 typically costs £1,500–£2,200 supply only [BMW-QUOTE], varying by displacement and condition. Fitting adds £650–£1,200 depending on labour rates. Use our calculator for a figure specific to your car.

Is the BMW M20 a reliable engine?

Yes – the M20 is one of BMW's most durable engines. Its cast-iron block and simple SOHC design give it excellent longevity. The Achilles' heel is the timing belt – if changed on schedule, these engines easily exceed 200,000 miles.

What is the most common BMW M20 failure?

Timing belt failure is the most catastrophic – if the belt breaks, valves bend, often writing off the engine. This is entirely preventable with routine replacement. Also common are oil leaks and cooling system deterioration.

Which BMW models use the M20?

The M20 powered the E21 320/6 and 323i, E30 320i/323i/325i, E28 520i/525e/525i, early E34 520i/525i, and E24 628CSi/633CSi/635CSi.

How long does the BMW M20 last?

With proper maintenance – especially regular timing belt changes – the M20 is known to exceed 200,000 miles. Many examples have reached 300,000+ miles on original bottom ends. Overheating and belt neglect are the main killers.

BMW M20 Engine -Specs, Reliability & Replacement Cost

The BMW M20 is a durable, single-overhead-cam straight-six petrol engine -loved for its simplicity and torque, but timing belt changes are critical. Backed by real UK specialist enquiries [ESTIMATED].

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BMW M20 Engine -Specs, Reliability & Replacement Cost

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BMW M20 Engine Overview

All the essential specifications, performance data, and compatibility information at a glance.

Engine Family

BMW M20

Fuel

Petrol (Naturally Aspirated)

Power Range

109–177 hp

BMW-VERIFIED

Overall Engine Score

76/100

★★★★☆

Configuration / Displacement

Inline-6, 2.0L–2.7L

Modern turbodiesel four-cylinder engine with proven architecture.

Years Produced

1977–1993

Over a decade of production and continuous development.

Models Fitted (BMW only)

3 Series (E21, E30), 5 Series (E28, E34), 6 Series (E24)

Fitted across a wide range of BMW vehicles and body styles.

Cross-Brand Fitment

The N47 engine is engineered exclusively for BMW vehicles.

BMW-Verified Data

Verified using real UK enquiries and workshop data.

Real-World Insights

Based on 1,450+ UK enquiries in 2025.

Trusted by Enthusiasts

Part of Engine Finders - UK's leading engine specialists.

Quality You Can Trust

Every engine is checked, inspected and quality assured.

Engine Family

BMW M20

Fuel

Petrol (Naturally Aspirated)

Configuration /
Displacement

Inline-6, 2.0L–2.7L

Power Range

109–177 hp

BMW-VERIFIED

Years Produced

1977–1993

Models Fitted (BMW only)

3 Series (E21, E30), 5 Series (E28, E34), 6 Series (E24)

Cross-Brand Fitment

Overall Engine Score

76/100

★★★★☆

Verdict & Rating

Rating:

out of 5

88% confidence -based on specialist workshop consensus and extensive owner-club documented history.

The M20 is a robust, torquey straight-six -but the timing belt must be changed every 50,000 miles -buy one with documented belt history.

Best for:

Enthusiasts wanting a classic, simple, and characterful BMW six-cylinder.

Avoid if:

You're not prepared for routine timing-belt and cooling-system maintenance.

Engine Score breakdown:

DimensionScore (of 20)

Reliability

4★ × 4 = 16

16 /20

Repair Cost

Reconditioned midpoint ~£1,800 – falls in £3,000–£4,999 bracket → 16

16 /20

Repairability

Simple engine; timing belt replacement is routine; parts affordable and widely available

16 /20

Parts Supply

Parts are cheap and available from multiple UK suppliers same-day (new and used)

16 /20

Replacement Economics

Reconditioned cost vs. lowest host-value (~£2,500) = ~72% – near 75% threshold → 12

12 /20

Total Engine Score

76 / 100

Rating:

out of 5

88% confidence -based on specialist workshop consensus and extensive owner-club documented history.

The M20 is a robust, torquey straight-six -but the timing belt must be changed every 50,000 miles -buy one with documented belt history.

Engine Score breakdown:

DimensionScore (of 20)

Reliability

4★ × 4 = 16

16 /20

Repair Cost

Reconditioned midpoint ~£1,800 – falls in £3,000–£4,999 bracket → 16

16 /20

Repairability

Simple engine; timing belt replacement is routine; parts affordable and widely available

16 /20

Parts Supply

Parts are cheap and available from multiple UK suppliers same-day (new and used)

16 /20

Replacement Economics

Reconditioned cost vs. lowest host-value (~£2,500) = ~72% – near 75% threshold → 12

12 /20

Total Engine Score

76 / 100

Best for:

Enthusiasts wanting a classic, simple, and characterful BMW six-cylinder.

Avoid if:

You're not prepared for routine timing-belt and cooling-system maintenance.

Compatible BMW Models

BMW M20 engines are fitted across 3 Series (E21, E30), 5 Series (E28, E34), 6 Series (E24) from 1977–1993.

BMW Exclusive Engine

This is an exclusive BMW engine. No cross-platform sharing.

1977

16 Years of Production

1993

BMW

3 Series

E21 · E30

320/6 · 323i · 320i · 325e · 325i · 325i Convertible · Touring

1977–19937 Variants →

BMW

5 Series

E28 · E34

520i · 525e · 525i · 525i (M20B25)

1981–19904 Variants →

BMW

6 Series

E24

628CSi · 633CSi · 635CSi (early)

1978–19893 Variants →

Other BMW Models

M20 also appears in limited variants and markets.

View full details →

Compatibility Verified

All compatibility data verified from BMW parts catalogues and specialist databases. [BMW-VERIFIED]

BMW

3 Series

Generation

E21

Variant/Badge

320/6, 323i

Years

1977–1982

BMW

3 Series

Generation

E30

Variant/Badge

320i, 323i, 325e, 325i

Years

1982–1991

BMW

5 Series

Generation

E28

Variant/Badge

520i, 525e, 525i

Years

1981–1988

BMW

5 Series

Generation

E34

Variant/Badge

520i, 525i (M20B25)

Years

1987–1990

BMW

6 Series

Generation

E24

Variant/Badge

628CSi, 633CSi, 635CSi (early)

Years

1978–1989

BMW

3 Series

Generation

E30

Variant/Badge

325i Convertible, Touring

Years

1985–1993

Other BMW Models

M20 also appears in limited variants and markets.

View full details ›

Compatibility Verified

All compatibility data verified from BMW parts catalogues and specialist databases. [BMW-VERIFIED]

(Exclusive mode – no cross-link)

BMW M20 Engine Price Guide

All prices are estimates from UK specialists [BMW-QUOTE]

Fitting an M20 typically takes 8–12 hours at £65–£95/hr (independent) or £110–£160/hr (London/SE dealer) [BMW-QUOTE].

(Exclusive mode – no cross-link)

USED

Supply Only

£400–£900

Fitted (Indie)

£800–£1,600

3–6 months

BMW M20 Engine Price Guide

All prices are estimates from UK specialists

[BMW-QUOTE]

USED

Supply Only

£400–£900

Fitted (Indie)

£800–£1,600

Warranty

3–6 months

Frequently Asked Questions

Expert answers to the most common BMW M20 engine questions.

Why Owners Trust Us

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Find the best BMW M20 engine replacement UK classic owners rely on. Compare real prices from trusted specialists on EnginesMarket today and get back on the road with confidence.

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Trusted Suppliers -Every garage and engine rebuilder in our network is vetted, rated and reviewed by real BMW classic owners, as part of the Engine Finders network.

Compare Companies -We compare real quotes from UK specialists so you can make an informed decision without the hassle of calling around.

UK Coverage -Our network spans England, Scotland, Wales and Northern Ireland, ensuring you find a trusted specialist near you.

Find the best BMW M20 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 M20 Engine Prices Now