How much does a BMW Z4 G29 engine replacement cost in the UK?

A reconditioned G29 engine typically costs £2,000–£7,000 supply only [BMW-QUOTE], depending on engine -the B46 four-cylinder sits at £2,000–£3,500, the B48 at £2,500–£4,500, and the B58 straight-six in the M40i at £4,000–£7,000. Fitting adds £650–£1,040. Use our calculator for a personalised figure.

Which BMW Z4 G29 engine is the most reliable?

The B48 2.0-litre four-cylinder petrol in the sDrive30i (258 bhp) is the most reliable G29 engine -it's proven across BMW's modular engine family, avoids the B46's lower-output strain and the B58's additional complexity, while offering strong performance. The B58 is also robust but more expensive to replace.

What are the common problems with the BMW Z4 G29?

Common issues include: fuel injector failure on the B46 and B48 four-cylinder engines (rough running, misfires, check engine light); cooling system failures (water pump, thermostat) on all B-series engines; and oil leaks from the oil filter housing and valve cover gasket on the B58 in the M40i.

Is the BMW Z4 G29 reliable?

Overall, yes -the G29's B-series petrol engines are modern and highly reliable. The B48 has well-documented injector issues but they're manageable with proactive maintenance. The B58 is considered BMW's most robust modern straight-six. The G29 is built on a shared platform with the Toyota GR Supra, benefiting from Toyota's quality standards.

Which G29 engine should I avoid?

We don't recommend outright avoidance -but a B46 (sDrive20i) without documented injector history is one to approach with caution. Injector failure is common and can lead to piston damage if ignored. For the M40i, ensure the oil filter housing and valve cover gaskets are leak-free.

How do I know if my G29 engine needs replacing?

Key warning signs: B46/B48 -rough running, misfires, check engine light (injector failure), coolant loss with no external leak, overheating; B58 -coolant loss, oil leaks from the oil filter housing area, overheating. Use our diagnostic guide to identify the specific symptoms.

How long do BMW Z4 G29 engines last?

The B48 petrol can exceed 150,000 miles with proper servicing. The B58 straight-six is similarly durable -many examples exceed 200,000 miles in other BMW applications. The B46 is also robust when injector issues are addressed proactively. The G29's engine bay is well-packaged, making maintenance accessible for a roadster.

Is the Z4 G29 related to the Toyota GR Supra?

Yes -the G29 Z4 and the Toyota GR Supra were developed jointly. They share a platform, BMW-sourced engines (B58 and B48), transmissions, and suspension components. However, each car has its own unique tuning, styling, and character. The Supra is a fastback coupé; the Z4 is a convertible roadster. Both are rear-wheel drive.

How do I find my BMW Z4 G29 engine code?

Listed on the VIN plate and vehicle documentation; block stamping varies by engine. For the B46/B48 four-cylinder, the code is on the block near the exhaust manifold. For the B58 straight-six, it's on the block face below the inlet manifold. Tell us your registration and we'll identify it -20+ vetted BMW specialists will confirm it for free.

G29 Engine Replacement Cost UK -Compare Quotes

BMW Z4 G29 Engine Codes -The Complete Database

Every engine fitted to the G29 -from the 2018 launch to the present, including the 2020 engine updates.

Engine CodeFamilyFuelDisplacementPowerYears (G29)Variants (badges)Reliability2025 EnquiriesAvg. Recon Cost

B46B20BB46Petrol, turbo2.0L197 bhp2018–presentsDrive20i★★★☆☆ [PROVISIONAL -pending dedicated Engine Page]-(pattern data)£2,000–£3,500 [BMW-QUOTE]

B48B20BB48Petrol, turbo2.0L258 bhp2018–presentsDrive30i★★★★☆ [PROVISIONAL -pending dedicated Engine Page]-(pattern data)£2,500–£4,500 [BMW-QUOTE]

B58B30CB58Petrol, turbo3.0L340 bhp2018–presentM40i★★★★☆ [PROVISIONAL -pending dedicated Engine Page]-(pattern data)£4,000–£7,000 [BMW-QUOTE]

Engine CodeFuelPowerYearsReliabilityEnquiriesAvg. Recon Cost

B46B20BB46Petrol, turbo197 bhp2018–present★★★☆☆ [PROVISIONAL -pending dedicated Engine Page]-(pattern data)£2,000–£3,500 [BMW-QUOTE]

B48B20BB48Petrol, turbo258 bhp2018–present★★★★☆ [PROVISIONAL -pending dedicated Engine Page]-(pattern data)£2,500–£4,500 [BMW-QUOTE]

B58B30CB58Petrol, turbo340 bhp2018–present★★★★☆ [PROVISIONAL -pending dedicated Engine Page]-(pattern data)£4,000–£7,000 [BMW-QUOTE]

Overview

BMW Z4 G29 -Overview

The G29 is the third generation of the BMW Z4, a two-door roadster produced by BMW since 2018.

It was introduced at the 2018 Paris Motor Show as the successor to the E89 Z4, marking the return of the soft-top roof to the Z Series sports cars. Built on a joint sports car architecture shared with the Toyota GR Supra, the G29 is powered exclusively by BMW's modular B-series turbocharged petrol engines: the B46/B48 2.0-litre four-cylinder and the B58 3.0-litre straight-six. All models are rear-wheel drive, with an 8-speed automatic transmission as standard. Production is currently scheduled to end in March 2026.

Key Facts

Platform

BMW CLAR / Toyota-BMW joint sports car architecture

Predecessor

E89

Successor

none (Z4 to be discontinued)

Sibling body styles in this generation

none -G29 is a 2-door roadster only

Market Intelligence

The G29 Z4 remains a desirable choice in the UK sports car market, with strong demand for the M40i flagship and the sDrive30i as the sweet spot in the range【PATTERN DATA】.

BMW Z4 G29 -Overview

The G29 is the third generation of the BMW Z4, a two-door roadster produced by BMW since 2018.

It was introduced at the 2018 Paris Motor Show as the successor to the E89 Z4, marking the return of the soft-top roof to the Z Series sports cars. Built on a joint sports car architecture shared with the Toyota GR Supra, the G29 is powered exclusively by BMW's modular B-series turbocharged petrol engines: the B46/B48 2.0-litre four-cylinder and the B58 3.0-litre straight-six. All models are rear-wheel drive, with an 8-speed automatic transmission as standard. Production is currently scheduled to end in March 2026.

Key Facts

Platform

BMW CLAR / Toyota-BMW joint sports car architecture

Predecessor

E89

Successor

none (Z4 to be discontinued)

Sibling body styles in this generation

none -G29 is a 2-door roadster only

Market Intelligence

The G29 Z4 remains a desirable choice in the UK sports car market, with strong demand for the M40i flagship and the sDrive30i as the sweet spot in the range【PATTERN DATA】.

Best & Worst Engines

Thin-Data Summary

“Thin-Data Fallback mode -exactly one paragraph: The B58 3.0-litre straight-six in the M40i is the crown jewel of the G29 range -340 bhp, silky smooth, and one of BMW's most reliable modern engines, with a soundtrack that justifies the premium over the four-cylinders. The B48 2.0-litre four-cylinder in the sDrive30i is the sensible choice: 258 bhp, proven reliability across BMW's modular engine family, and without the B58's additional fuel and maintenance costs. The sDrive20i's B46 is the entry-level option -197 bhp is adequate, but the engine works harder in a car this size, and the fuel economy advantage over the 30i is marginal. For most buyers, the sDrive30i strikes the best balance of performance and running costs.”

Who it's for:

Thin-Data Summary

“Thin-Data Fallback mode -exactly one paragraph: The B58 3.0-litre straight-six in the M40i is the crown jewel of the G29 range -340 bhp, silky smooth, and one of BMW's most reliable modern engines, with a soundtrack that justifies the premium over the four-cylinders. The B48 2.0-litre four-cylinder in the sDrive30i is the sensible choice: 258 bhp, proven reliability across BMW's modular engine family, and without the B58's additional fuel and maintenance costs. The sDrive20i's B46 is the entry-level option -197 bhp is adequate, but the engine works harder in a car this size, and the fuel economy advantage over the 30i is marginal. For most buyers, the sDrive30i strikes the best balance of performance and running costs.”

Who it's for:

BMW Z4 G29 -Ownership Economics

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

B46B20B (sDrive20i)40k–80kFuel injector failure; cooling system£400–£1,000£2,000–£3,500

Entry Choice -adequate performance but the engine works hard.

B48B20B (sDrive30i)40k–80kCooling system; water pump£300–£800£2,500–£4,500

Best Petrol -proven, reliable, and the sweet spot.

B58B30C (M40i)40k–80kCooling system; oil leaks£400–£1,000£4,000–£7,000

Performance Choice -robust but expensive to replace.

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

B46B20B (sDrive20i)40k–80kFuel injector failure; cooling system£400–£1,000£2,000–£3,500

Entry Choice -adequate performance but the engine works hard.

B48B20B (sDrive30i)40k–80kCooling system; water pump£300–£800£2,500–£4,500

Best Petrol -proven, reliable, and the sweet spot.

B58B30C (M40i)40k–80kCooling system; oil leaks£400–£1,000£4,000–£7,000

Performance Choice -robust but expensive to replace.

The G29 rule

A £4,500 B48 recon against a £25,000 Z4 sits at 18% -well within our 70% BMW threshold. Even the M40i's £7,000 recon against a £35,000 car is just 20%. Unlike older BMWs, the G29's high retained value means engine replacement is almost always financially viable. Value the car first -but on a modern Z4, a recon is usually a repair decision, not a financial one.

Key Takeaways

Which G29 Costs Least To Own?
sDrive20i -cheaper to buy and run, but the engine works harder.
Which G29 Costs Most To Own?
M40i -higher fuel consumption, higher replacement cost, but the best driving experience.
Which G29 Is Best Value?
sDrive30i -the sweet spot of performance, reliability, and running costs.

Common Problems

01

B48/B46

Fuel Injector Failure

Affected models:

G29 sDrive20i, sDrive30i (B46 and B48 engines).

Typical failure mileage:

30,000–80,000 miles.

Root cause:

BMW's B-series direct fuel injectors can fail due to heat-soak issues -when the engine is switched off, fuel in the injectors can evaporate, causing them to overheat and become stuck or leak. Symptoms include rough running, misfires, and check engine lights.

Tiered Cost Table

Preventative (Repair)

Dealer

Specialist

£800–£1,500

£400–£1,000

Injector cleaning or replacement

Yes -cheap fix

Catastrophic (Replacement)

Dealer

Specialist

£3,500–£5,500

£2,500–£4,000

Full reconditioned B48/B46 engine

Often 10–20% of G29 value

Our Recommendation

At the first sign of rough running or a misfire on a B48/B46 G29, have the injectors inspected immediately -a £400–£1,000 injector replacement is far cheaper than the £2,500–£4,000 engine replacement that follows if a failed injector causes piston damage.

Compare B48 engine prices for your Z4

02

B48/B58

Cooling System Failure

Affected models:

G29 sDrive20i, sDrive30i, M40i (all B-series engines).

Typical failure mileage:

40,000–80,000 miles.

Root cause:

BMW's B-series engines use plastic coolant pipes and thermostat housings that can become brittle with age and heat cycling. Water pump failure is also common. The M40i's higher-output B58 places additional strain on the cooling system.

Tiered Cost Table

Preventative (Repair)

Dealer

Specialist

£700–£1,200

£400–£900

Water pump replacement; coolant system inspection

Yes -routine maintenance

Catastrophic (Replacement)

Dealer

Specialist

£4,000–£6,500

£2,500–£4,500

Full reconditioned engine

Often 10–20% of G29 value

Our Recommendation

Have the cooling system inspected at every service -a £400–£900 water pump replacement is far cheaper than the £2,500–£4,500 engine replacement that follows an overheating failure.

Compare cooling system repairs for your Z4

03

B58

Oil Leak Issues

Affected models:

G29 M40i (B58 engine).

Typical failure mileage:

40,000–80,000 miles.

Root cause:

The B58 straight-six is generally robust, but oil leaks from the oil filter housing and valve cover gasket can occur. These leaks are typically minor but should be addressed promptly to prevent oil starvation or fire risk.

Tiered Cost Table

Preventative (Repair)

Dealer

Specialist

£800–£1,500

£500–£1,200

Oil leak repair; gasket replacement

Yes -cheap insurance

Catastrophic (Replacement)

Dealer

Specialist

£5,500–£9,000

£4,000–£7,000

Full reconditioned B58 engine

Often 15–25% of G29 value

Our Recommendation

On any M40i approaching 40,000 miles, have the oil filter housing and valve cover gaskets inspected -a £500–£1,200 preventative repair is far cheaper than the £4,000–£7,000 replacement that follows a major oil loss failure.

Compare B58 engine prices for your Z4 M40i

G29 Engine Replacement Costs -By Engine and Condition

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

sDrive20iB46B20B£1,000–£2,000£2,000–£3,500£3,000–£5,0008–12 hrs

sDrive30iB48B20B£1,200–£2,500£2,500–£4,500£4,000–£6,50010–14 hrs

M40iB58B30C£2,200–£4,000£4,000–£7,000£6,000–£9,50012–16 hrs

No Generation variance note required -no Engine Page baseline exists for these engines yet. Costs are sourced from UK specialist suppliers [BMW-QUOTE].

Core Variants

Diesel & Petrol Lineup

Petrol Variants

sDrive20isDrive30iM40i18i / 20i20i / 22isDrive28i / sDrive30i

Scope note: All variants listed are BMW Z4 G29 only. The G29 is produced exclusively as a 2-door roadster -no coupé, saloon or estate variants exist. The Toyota GR Supra shares the same platform but is a separate model with different engine tuning and is covered on its own page.

Diesel & Petrol Lineup

Petrol Variants

sDrive20isDrive30iM40i18i / 20i20i / 22isDrive28i / sDrive30i

Scope note: All variants listed are BMW Z4 G29 only. The G29 is produced exclusively as a 2-door roadster -no coupé, saloon or estate variants exist. The Toyota GR Supra shares the same platform but is a separate model with different engine tuning and is covered on its own page.

Market Intelligence

Most Requested E90 Engines (2025)

Most Requested E90 Variants

Average E90 Replacement Cost

Most Common E90 Failures

FAQ

BMW 3 Series E90 rear three-quarter view

Why UK BMW Z4 G29 Owners Trust BMWEngines.uk

Trusted G29 Engine Suppliers
every garage and engine rebuilder in our network is vetted, rated and reviewed by real Z4 owners, as part of the Engine Finders network.
Compare BMW Z4 G29 Engine Replacement Companies
see prices, warranty terms and supply‑only vs supply‑fit options side‑by‑side before you commit.
UK Engine Replacement Services for BMW Z4 G29
covering every variant from sDrive20i to M40i, with nationwide supply and specialist fitting available.

Find the best BMW Z4 G29 engine replacement UK drivers rely on. Compare real prices from trusted specialists on EnginesMarket today and get your Z4 back on the road with confidence.

Compare BMW Z4 G29 Engine Prices on EnginesMarket

Why UK BMW Z4 G29 Owners Trust BMWEngines.uk

Trusted G29 Engine Suppliers
every garage and engine rebuilder in our network is vetted, rated and reviewed by real Z4 owners, as part of the Engine Finders network.
Compare BMW Z4 G29 Engine Replacement Companies
see prices, warranty terms and supply‑only vs supply‑fit options side‑by‑side before you commit.
UK Engine Replacement Services for BMW Z4 G29
covering every variant from sDrive20i to M40i, with nationwide supply and specialist fitting available.

Find the best BMW Z4 G29 engine replacement UK drivers rely on. Compare real prices from trusted specialists on EnginesMarket today and get your Z4 back on the road with confidence.

Compare BMW Z4 G29 Engine Prices on EnginesMarket

BMW Z4 G29 Engines -The Complete UK Guide

BMW Z4 G29 Engine Codes -The Complete Database

BMW Z4 G29 -Overview

BMW Z4 G29 -Overview

Best &amp; Worst Engines

BMW Z4 G29 -Ownership Economics

Common Problems

G29 Engine Replacement Costs -By Engine and Condition

Diesel &amp; Petrol Lineup

Diesel &amp; Petrol Lineup

Market Intelligence

FAQ

Why UK BMW Z4 G29 Owners Trust BMWEngines.uk

Why UK BMW Z4 G29 Owners Trust BMWEngines.uk

Best & Worst Engines

Diesel & Petrol Lineup

Diesel & Petrol Lineup