BMW 3 Series G20 Engines -The Complete UK Guide
Every engine fitted to the seventh-generation 3 Series G20 saloon -from the 2.0-litre B48 four-cylinder to the 3.0-litre B58 six-cylinder, the plug-in hybrid 330e and the range-topping M340i. Real UK costs, honest reliability data, and BMW's modular engine family at its best. Backed by 190+ real UK G20 enquiries in 2025 [BMW-VERIFIED].
Explore G20 Engines
BMW 3 Series G20 Engine Codes -The Complete Database
Every engine fitted to the G20 saloon specifically -from the entry-level 318i to the M340i, including the B48-to-B58 modular engine family and the plug-in hybrid 330e.
Overview
BMW 3 Series G20 -Overview
The seventh-generation BMW 3 Series (codenamed G20 for the saloon) was unveiled at the 2018 Paris Motor Show on 2 October 2018 and entered production later that month.
Built on BMW's CLAR platform, the G20 marked a significant evolution over the F30 -lighter, stiffer and more technologically advanced. The engine range launched with 2.0-litre B48 four-cylinder petrols (320i, 330i) and the 3.0-litre B58 six-cylinder (M340i), joined by B47 four-cylinder and B57 six-cylinder diesels. A plug-in hybrid 330e arrived in 2019, and a July 2022 facelift (LCI) brought mild-hybrid technology to the range. The M3 (G80), based on the G20 platform, uses the S58 engine and is covered on its own Generation Page.
Key Facts
Platform
BMW CLAR (Cluster Architecture)
Predecessor
BMW 3 Series F30
Successor
Current (in production)
Sibling body styles in this generation
G21 Touring, G28 Long-Wheelbase Saloon, G80 M3
Market Intelligence
The G20 saloon generated 190 real UK engine enquiries in 2025 [BMW-VERIFIED], concentrated on the 320i and 330i as the most popular UK variants.
Best & Worst Engines
Best Petrol Overall
B48B20B -330i (2018–2026)
“The B48 is BMW's most refined four-cylinder -smooth, responsive and genuinely reliable. The 330i's 258 PS is the sweet spot: more powerful than the 320i, but without the complexity or running costs of the six-cylinder M340i.”
Who it's for: buyers who want the best all-round G20 petrol.
Highest Risk
B48B20A (PHEV) -330e
“The 330e adds complexity -electric motor, battery pack and charging system -to the otherwise robust B48. Battery health and charging system reliability are the key concerns; hybrids are more complex to maintain.”
Who it's for: buyers who want company-car tax benefits and are prepared for hybrid-specific maintenance.
Most Expensive Failure
S58B30A -M3/M3 Competition
“The S58 is a high-performance engine with significant complexity -twin turbos, high-pressure fuel system and M-specific components. Repairs are specialist-only and expensive; full replacement costs £8,000–£14,000.”
Who it's for: enthusiasts who want 510 PS and are ready for the bills that come with it.
Best Value
B48B20A -320i (2018–2026)
“The 320i is the most common G20 petrol -reliable, efficient and well-supported. A £2,800–£4,500 recon makes sense against a £15,000–£30,000 vehicle.”
Who it's for: buyers who want the most cost-effective G20 ownership.
Most Overlooked
B47D20B -320d
“The B47 is a significant improvement over the N47 -timing chain issues are far less common, and EGR cooler problems are well-documented and manageable. The 320d offers excellent economy without the petrol's fuel bills.”
Who it's for: buyers who want diesel economy and don't need six-cylinder pace.
BMW 3 Series G20 -Ownership Economics
The G20 rule
A £3,200–£5,000 B48 recon against a £15,000–£35,000 G20 sits at 9–33% of the car's value -well within our 70% BMW threshold. Even against a sub-£12,000 high-mileage example, the same recon is 27–42% -a repair decision, not a financial one. The G20 holds value well enough that engine replacement is almost always viable.
Common Problems
G20 Engine Replacement Costs -By Engine and Condition
No Generation variance from the Engine Page baseline -no dedicated Engine Pages exist for these families yet, so baseline figures are drawn from the EM_Proprietary_Data Table A. Labour hours estimated at 10–14 hours for four-cylinder engines, 12–16 hours for six-cylinder engines, and 16–22 hours for the M3's S58 due to additional complexity.
Core Variants
Diesel & Petrol Lineup
Scope note: All variants listed are G20 saloon only. The G21 Touring and G28 long-wheelbase saloon share most of these engines but are covered on their own Generation Pages. The M3 (G80) is based on the G20 platform but uses the S58 engine; it is covered on its own Generation Page. The 330e PHEV uses the B48B20A engine with an electric motor.
Market Intelligence
Most Requested E90 Engines (2025)
- 1.1. B48B20A 320i -930 requests [BMW-VERIFIED]
- 2.2. B48B20B 330i -540 requests [BMW-VERIFIED]
- 3.3. B58B30B M340i -540 requests [BMW-VERIFIED]
Most Requested E90 Variants
- 1.1. 320i
- 2.2. 330i
- 3.3. M340i
Average E90 Replacement Cost
£4,500 reconditioned, supply only [BMW-QUOTE]
Most Common E90 Failures
- 1.1. Cooling system leaks (B-series)
- 2.2. EGR cooler (B47 diesel)
- 3.3. Battery/charging system (330e PHEV)
BMW 320i
G20 (B48)
5
enquiries
BMW 330e
G20 (B48 PHEV)
3
enquiries
BMW M340i
G20 (B58)
3
enquiries
FAQ
Why UK BMW 3 Series G20 Owners Trust BMWEngines.uk
Trusted G20 Engine Suppliers
every garage and engine rebuilder in our network is vetted, rated and reviewed by real 3 Series owners, as part of the Engine Finders network.
Compare G20 Engine Replacement Companies
see prices, warranty terms and supply & fit options side-by-side before you commit.
UK Engine Replacement Services for G20
covering every variant from 318i to M3, with supply-only or full supply & fit available nationwide.
Find the best BMW 3 Series G20 engine replacement UK drivers rely on. Compare real prices from trusted specialists on EnginesMarket today and get back on the road with confidence.
