BMW Z4 G29Roadster2018–present

BMW Z4 G29 Engines — The Complete UK Guide

Every engine fitted to the third-generation Z4 roadster — from the 2.0-litre B48 four-cylinder petrols to the 3.0-litre B58 straight-six in the M40i.

Real UK replacement costs, honest failure data, and the cooling system and fuel injector issues that define this generation's ownership story.

Backed by real UK enquiry data [PATTERN DATA].

Explore G29 Engines
  • G29 Enquiries (Pattern Data)
  • RoadsterBody Style
  • 4Engine CodesCovered
  • Part ofEngine FindersUK's #1 Engine Marketplace

Engine Database

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 CodeFuelPowerYearsReliabilityEnquiries (2025)Avg. Recon Cost
B46B20BB46PetrolTurbo197 bhp2018–present★★★☆☆PROVISIONALpending dedicated Engine Page—(pattern data)£2,000–£3,500[BMW-QUOTE]
B48B20BB48PetrolTurbo258 bhp2018–present★★★★☆PROVISIONALpending dedicated Engine Page—(pattern data)£2,500–£4,500[BMW-QUOTE]
B58B30CB58PetrolTurbo340 bhp2018–present★★★★☆PROVISIONALpending dedicated Engine Page—(pattern data)£4,000–£7,000[BMW-QUOTE]
BMW Z4 G29 -Overview

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

  • PlatformBMW CLAR / Toyota-BMW joint sports car architecture
  • PredecessorE89
  • Successornone (Z4 to be discontinued)
  • Sibling Body Styles in this Generationnone — 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】.

04Best & Worst Engines

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.

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.

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

G29
Engine Replacement Costs -By Engine and Condition

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

Diesel & Petrol Lineup

Petrol Variants

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 Engines (2025)

    Most Requested Variants

      Average Replacement Cost

      Most Common Failures

        FAQ

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