How much does a BMW 4 Series G23 engine replacement cost in the UK?

A reconditioned G23 engine typically costs £2,500–£8,000 supply only, depending on the engine -the B48 four-cylinder sits at £2,500–£5,000, the B58 six-cylinder is £4,000–£7,000, and the B57 diesel six-cylinder is £4,500–£8,000. Fitting adds £650–£1,500. Use our calculator for a personalised figure.

Which BMW 4 Series G23 engine is the most reliable?

The B58B30B in the M440i xDrive is the most reliable engine in the G23 range -BMW's modular straight-six is chain-driven, robust, and widely regarded as one of BMW's most dependable modern engines. On the diesel side, the B47D20B in the 420d is the most reliable four-cylinder diesel option, with an accessible front-mounted timing chain.

What are the common problems with the BMW 4 Series G23?

On B48 petrol engines, coolant leaks from the expansion tank and water pump are the most common issues. On 48V mild-hybrid equipped models (M440i, 420d, 430d, M440d), system integration issues can occur. The B47 diesel in the 420d can suffer from DPF clogging with urban use. The fabric soft top mechanism is the most common non-engine issue.

Is the BMW 4 Series G23 reliable?

The G23 uses BMW's proven modular B-series engine family -the B48, B58, B47, and B57 have established reliability records across the BMW range. The B58 is widely regarded as one of BMW's most reliable engines. The 48V mild-hybrid system is relatively new but has proven reliable in other BMW models. As a newer model, long-term G23-specific data is limited, but the engine family is well-proven.

Which BMW 4 Series G23 engine should I avoid?

We don't say 'avoid' outright -all G23 engines are from the proven B-series family. For buyers who prioritise efficiency, the B47 diesel is the best choice. For performance buyers, the B58 in the M440i xDrive is the standout. The 420i is the entry-level choice. All are reliable when properly maintained.

How do I know if my G23 engine needs replacing?

Major failures are unlikely in the early years. Watch for check engine lights, loss of power, misfires, or unusual noises. On B48 models, coolant leaks and overheating warnings are the key signs. On 48V MHEV models, reduced assistance or warning lights may indicate system issues. On diesel models, DPF warning lights indicate regeneration issues. Use our diagnostic calculator for a personalised assessment.

Is it worth replacing a BMW 4 Series G23 engine, or should I scrap the car?

As a premium convertible with values above £25,000, a £4,000–£7,000 engine replacement is 16–28% of the car's value -well within our 70% BMW threshold. Replacement is almost always financially viable. Extended warranty cover is strongly recommended, especially for 48V mild-hybrid system components and the fabric roof mechanism.

How long do BMW 4 Series G23 engines last?

The B58 six-cylinder can exceed 200,000 miles with proper servicing -it's one of BMW's most durable modern engines. The B48 and B47 fours are also capable of 150,000+ miles. The B57 diesel six is similarly robust but more complex. As with any modern BMW, strict oil change intervals are the key to longevity.

What is the difference between the G22 and G23?

The G22 and G23 are the same generation of BMW 4 Series -the G22 is the 2-door coupé, while the G23 is the 2-door convertible. Both share the same platform, engine range, and interior. The G23 replaces the F33's folding hardtop with a fabric soft top, saving approximately 40% weight. This page covers the G23 specifically, but all engine data applies equally to the G22.

How do I find my BMW 4 Series G23 engine code?

Listed on the VIN plate and vehicle documentation; the engine code is also stamped on the cylinder block. Common G23 codes include B48B20M0 (420i), B48B20O1 (430i), B58B30B/TÜ1 (M440i xDrive), B47D20B (420d), B57D30A (430d), and B57D30B (M440d xDrive). Tell us your variant and registration date and we'll identify it for you.

G23 Engine Replacement Cost UK -Compare Quotes

Name: BMW 4 Series G23 UK Engine Enquiry Data 2025
Creator: bmwengines.uk

BMW 4 Series G23 Engine Codes -The Complete Database

Every engine fitted to the G23 convertible -from the entry‑level 420i to the range‑topping M440i xDrive, and the full diesel range including the B57 straight‑six.

Engine CodeFamilyFuelDisplacementPowerYears (G23)

VariantsReliability2025 EnquiriesAvg. Recon CostB48B20M0B48

Petrol2.0L (1998 cc)135 kW (184 PS; 181 hp) / 300 Nm2020–present420i★★★★☆ [PROVISIONAL -pattern data]

540 (B58 JLR‑wide) [EM‑VERIFIED]£2,500–£4,500 [BMW‑QUOTE]B48B20O1B48Petrol2.0L (1998 cc)

190 kW (258 PS; 255 hp) / 400 Nm2021–present430i, 430i xDrive★★★★☆ [PROVISIONAL -pattern data]540 (B58 JLR‑wide) [EM‑VERIFIED]£2,800–£5,000 [BMW‑QUOTE]

B48B20AB48Petrol2.0L (1998 cc)135–190 kW (184–258 PS)2020–present

420i, 430i★★★★☆ [PROVISIONAL -pattern data]540 (B58 JLR‑wide) [EM‑VERIFIED]£2,500–£5,000 [BMW‑QUOTE]B58B30BB58

Petrol + 48V MHEV3.0L (2998 cc)285 kW (388 PS; 382 hp) / 500 Nm2021–presentM440i xDrive★★★★★ [PROVISIONAL -pattern data]

540 (B58 JLR‑wide) [EM‑VERIFIED]£4,000–£7,000 [BMW‑QUOTE]B58B30TÜ1B58Petrol + 48V MHEV3.0L (2998 cc)

285 kW (388 PS; 382 hp) / 500 Nm2024–presentM440i xDrive (LCI)★★★★★ [PROVISIONAL -pattern data]540 (B58 JLR‑wide) [EM‑VERIFIED]£4,000–£7,000 [BMW‑QUOTE]

B47D20BB47Diesel + 48V MHEV2.0L (1995 cc)140 kW (190 PS; 187 hp) / 400 Nm2021–present

420d, 420d xDrive★★★★☆ [PROVISIONAL -pattern data]930 (B47 JLR‑wide) [EM‑VERIFIED]£2,800–£4,500 [BMW‑QUOTE]B57D30AB57

Diesel + 48V MHEV3.0L (2993 cc)207 kW (282 PS; 278 hp) / 650 Nm2021–present430d, 430d xDrive★★★★☆ [PROVISIONAL -pattern data]

830 (N57/B57 JLR‑wide) [EM‑VERIFIED]£4,500–£7,500 [BMW‑QUOTE]B57D30BB57Diesel + 48V MHEV3.0L (2993 cc)

250 kW (340 PS; 335 hp) / 700 Nm2021–presentM440d xDrive★★★★☆ [PROVISIONAL -pattern data]830 (N57/B57 JLR‑wide) [EM‑VERIFIED]£5,000–£8,000 [BMW‑QUOTE]

Engine CodeFuelPowerYearsReliabilityEnquiriesAvg. Recon Cost

VariantsReliability2025 EnquiriesB48B20M0B48

Petrol2.0L (1998 cc)135 kW (184 PS; 181 hp) / 300 Nm420i★★★★☆ [PROVISIONAL -pattern data]

540 (B58 JLR‑wide) [EM‑VERIFIED]£2,500–£4,500 [BMW‑QUOTE]B48B20O1Petrol2.0L (1998 cc)

190 kW (258 PS; 255 hp) / 400 Nm2021–present430i, 430i xDrive540 (B58 JLR‑wide) [EM‑VERIFIED]£2,800–£5,000 [BMW‑QUOTE]

B48B20AB48Petrol135–190 kW (184–258 PS)2020–present

420i, 430i★★★★☆ [PROVISIONAL -pattern data]540 (B58 JLR‑wide) [EM‑VERIFIED]B58B30BB58

Petrol + 48V MHEV3.0L (2998 cc)285 kW (388 PS; 382 hp) / 500 NmM440i xDrive★★★★★ [PROVISIONAL -pattern data]

540 (B58 JLR‑wide) [EM‑VERIFIED]£4,000–£7,000 [BMW‑QUOTE]B58B30TÜ1Petrol + 48V MHEV3.0L (2998 cc)

285 kW (388 PS; 382 hp) / 500 Nm2024–presentM440i xDrive (LCI)540 (B58 JLR‑wide) [EM‑VERIFIED]£4,000–£7,000 [BMW‑QUOTE]

B47D20BB47Diesel + 48V MHEV140 kW (190 PS; 187 hp) / 400 Nm2021–present

420d, 420d xDrive★★★★☆ [PROVISIONAL -pattern data]930 (B47 JLR‑wide) [EM‑VERIFIED]B57D30AB57

Diesel + 48V MHEV3.0L (2993 cc)207 kW (282 PS; 278 hp) / 650 Nm430d, 430d xDrive★★★★☆ [PROVISIONAL -pattern data]

830 (N57/B57 JLR‑wide) [EM‑VERIFIED]£4,500–£7,500 [BMW‑QUOTE]B57D30BDiesel + 48V MHEV3.0L (2993 cc)

250 kW (340 PS; 335 hp) / 700 Nm2021–presentM440d xDrive830 (N57/B57 JLR‑wide) [EM‑VERIFIED]£5,000–£8,000 [BMW‑QUOTE]

Overview

BMW 4 Series G23 -Overview

The BMW 4 Series G23 is the convertible variant of the second‑generation 4 Series, unveiled in September 2020.

It replaced the folding hardtop of its F33 predecessor with a fabric soft top, saving approximately 40% weight over the previous roof mechanism. Built on BMW's CLAR platform and manufactured in Dingolfing, Germany, the G23 shares its engine line‑up with the G22 coupé. The range includes B48 four‑cylinder petrol engines in the 420i and 430i, the B58 straight‑six in the M440i xDrive, and B47/B57 diesel options in the 420d, 430d and M440d xDrive. A 2024 facelift (LCI) brought updated engine codes and the Curved Display with OS 8.5.

Key Facts

Platform

BMW CLAR

Predecessor

BMW 4 Series F33 Convertible

Successor

None (current generation)

Sibling body styles in this generation

G22 Coupé, G26 Gran Coupé

Market Intelligence

The G23 shares its engine line‑up with the G22 -B58 enquiries totalled 540 and B47 enquiries totalled 930 in 2025 [EM‑VERIFIED], with the M440i xDrive attracting the highest proportion of performance‑oriented enquiries.

BMW 4 Series G23 -Overview

The BMW 4 Series G23 is the convertible variant of the second‑generation 4 Series, unveiled in September 2020.

It replaced the folding hardtop of its F33 predecessor with a fabric soft top, saving approximately 40% weight over the previous roof mechanism. Built on BMW's CLAR platform and manufactured in Dingolfing, Germany, the G23 shares its engine line‑up with the G22 coupé. The range includes B48 four‑cylinder petrol engines in the 420i and 430i, the B58 straight‑six in the M440i xDrive, and B47/B57 diesel options in the 420d, 430d and M440d xDrive. A 2024 facelift (LCI) brought updated engine codes and the Curved Display with OS 8.5.

Key Facts

Platform

BMW CLAR

Predecessor

BMW 4 Series F33 Convertible

Successor

None (current generation)

Sibling body styles in this generation

G22 Coupé, G26 Gran Coupé

Market Intelligence

The G23 shares its engine line‑up with the G22 -B58 enquiries totalled 540 and B47 enquiries totalled 930 in 2025 [EM‑VERIFIED], with the M440i xDrive attracting the highest proportion of performance‑oriented enquiries.

Best & Worst Engines

Best Diesel Overall

B57D30B (M440d xDrive, 2021–present)

““The 3.0‑litre twin‑turbo straight‑six diesel produces 340 PS and 700 Nm -effortless, refined, and with 48V mild‑hybrid assistance for stop‑start smoothness. It’s the diesel you buy if you want six‑cylinder torque and genuine pace.” Who it’s for: buyers who want diesel economy with M Performance pace.”

Who it's for:

Best Petrol Overall

B58B30B / B58B30TÜ1 (M440i xDrive, 2021–present)

““BMW’s modular straight‑six masterpiece -382 hp, 500 Nm, silky smooth, and chain‑driven with a robust bottom end. The B58 is widely regarded as one of BMW’s most reliable modern engines. In the G23 convertible, it’s the engine that defines the open‑top experience.” Who it’s for: buyers who want six‑cylinder performance and the ultimate open‑top soundtrack. (Model-wide: B58B30 is the benchmark across the BMW range -the G23 offers the best expression of it in a convertible.)”

Who it's for:

Highest Risk

B48B20M0 (420i, early production)

““The B48 is a robust engine overall, but early production units can suffer from coolant leaks from the expansion tank and water pump plastic fittings. These are relatively inexpensive repairs, but they’re the most common B48 issues.” Who it’s for: buyers who want entry‑level 4 Series ownership with a budget for cooling system maintenance.”

Who it's for:

Most Expensive Failure

B57D30B (M440d xDrive)

““A 340 PS twin‑turbo straight‑six diesel with complex 48V mild‑hybrid integration. If the turbochargers or hybrid system fail, repair costs can be significant -replacement cost sits at £5,000–£8,000. The B57 is a robust engine, but it’s complex.” Who it’s for: buyers who want diesel performance with a budget for high‑end maintenance.”

Who it's for:

Best Value

B48B20O1 (430i, 2021–present)

““255 hp and 400 Nm from a 2.0‑litre four‑cylinder -the sweet spot of the petrol range. It’s significantly more powerful than the 420i, but shares the B48’s proven reliability and relatively affordable running costs.” Who it’s for: buyers who want performance without the M440i’s premium.”

Who it's for:

Most Overlooked

B47D20B (420d, 2021–present)

““The 420d’s 2.0‑litre four‑cylinder diesel is the most efficient engine in the range, returning up to 56 mpg with 48V mild‑hybrid assistance. The B47 is chain‑driven with an accessible front‑mounted chain -none of the N47’s rear‑chain anxiety.” Who it’s for: high‑mileage buyers who prioritise economy and reliability.”

Who it's for:

Best Diesel Overall

B57D30B (M440d xDrive, 2021–present)

““The 3.0‑litre twin‑turbo straight‑six diesel produces 340 PS and 700 Nm -effortless, refined, and with 48V mild‑hybrid assistance for stop‑start smoothness. It’s the diesel you buy if you want six‑cylinder torque and genuine pace.” Who it’s for: buyers who want diesel economy with M Performance pace.”

Who it's for:

Best Petrol Overall

B58B30B / B58B30TÜ1 (M440i xDrive, 2021–present)

““BMW’s modular straight‑six masterpiece -382 hp, 500 Nm, silky smooth, and chain‑driven with a robust bottom end. The B58 is widely regarded as one of BMW’s most reliable modern engines. In the G23 convertible, it’s the engine that defines the open‑top experience.” Who it’s for: buyers who want six‑cylinder performance and the ultimate open‑top soundtrack. (Model-wide: B58B30 is the benchmark across the BMW range -the G23 offers the best expression of it in a convertible.)”

Who it's for:

Highest Risk

B48B20M0 (420i, early production)

““The B48 is a robust engine overall, but early production units can suffer from coolant leaks from the expansion tank and water pump plastic fittings. These are relatively inexpensive repairs, but they’re the most common B48 issues.” Who it’s for: buyers who want entry‑level 4 Series ownership with a budget for cooling system maintenance.”

Who it's for:

Most Expensive Failure

B57D30B (M440d xDrive)

““A 340 PS twin‑turbo straight‑six diesel with complex 48V mild‑hybrid integration. If the turbochargers or hybrid system fail, repair costs can be significant -replacement cost sits at £5,000–£8,000. The B57 is a robust engine, but it’s complex.” Who it’s for: buyers who want diesel performance with a budget for high‑end maintenance.”

Who it's for:

Best Value

B48B20O1 (430i, 2021–present)

““255 hp and 400 Nm from a 2.0‑litre four‑cylinder -the sweet spot of the petrol range. It’s significantly more powerful than the 420i, but shares the B48’s proven reliability and relatively affordable running costs.” Who it’s for: buyers who want performance without the M440i’s premium.”

Who it's for:

Most Overlooked

B47D20B (420d, 2021–present)

““The 420d’s 2.0‑litre four‑cylinder diesel is the most efficient engine in the range, returning up to 56 mpg with 48V mild‑hybrid assistance. The B47 is chain‑driven with an accessible front‑mounted chain -none of the N47’s rear‑chain anxiety.” Who it’s for: high‑mileage buyers who prioritise economy and reliability.”

Who it's for:

BMW 4 Series G23 -Ownership Economics

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

B48B20M0 (420i)60k–120kCoolant leaks (expansion tank / water pump)£400–£800£2,500–£4,500

Solid Choice -efficient, proven B48

B48B20O1 (430i)80k–150kCoolant leaks (less common than 420i)£400–£800£2,800–£5,000

Best Petrol Value -255 hp, proven B48

B58B30B/TÜ1 (M440i)80k–150kGeneral wear -B58 proven robust£500–£1,000£4,000–£7,000

Best Petrol -382 hp, the M440i’s defining asset

B47D20B (420d)80k–150kDPF clogging (urban use)£300–£600£2,800–£4,500

Best Diesel Value -efficient, chain accessible

B57D30A (430d)80k–150kGeneral wear -B57 proven robust£500–£1,200£4,500–£7,500

Solid Choice -282 hp, six‑cylinder refinement

B57D30B (M440d)80k–150kTurbocharger wear / 48V system issues£500–£1,500£5,000–£8,000

Performance Diesel -340 hp, complex but rewarding

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

B48B20M0 (420i)60k–120kCoolant leaks (expansion tank / water pump)£400–£800£2,500–£4,500

Solid Choice -efficient, proven B48

B48B20O1 (430i)80k–150kCoolant leaks (less common than 420i)£400–£800£2,800–£5,000

Best Petrol Value -255 hp, proven B48

B58B30B/TÜ1 (M440i)80k–150kGeneral wear -B58 proven robust£500–£1,000£4,000–£7,000

Best Petrol -382 hp, the M440i’s defining asset

B47D20B (420d)80k–150kDPF clogging (urban use)£300–£600£2,800–£4,500

Best Diesel Value -efficient, chain accessible

B57D30A (430d)80k–150kGeneral wear -B57 proven robust£500–£1,200£4,500–£7,500

Solid Choice -282 hp, six‑cylinder refinement

B57D30B (M440d)80k–150kTurbocharger wear / 48V system issues£500–£1,500£5,000–£8,000

Performance Diesel -340 hp, complex but rewarding

The G23 rule

A £4,000–£7,000 B58 recon against a £25,000–£50,000 G23 sits at 8–28% of the car’s value -well within our 70% BMW threshold. Even the most expensive engine replacement (M440d at £5,000–£8,000) is only 10–32% of a well‑kept G23’s value. The G23 is a premium convertible with strong retained values -replacement is almost always financially viable. Extended warranty cover is still recommended, especially for 48V mild‑hybrid system components.

Common Problems

01

B48

Coolant Leaks (Expansion Tank / Water Pump)

Affected models:

G23 420i, 430i (B48 four‑cylinder petrol).

B48 Coolant Leaks (Expansion Tank / Water Pump)

Typical failure mileage:

60,000–100,000 miles.

Root cause:

The B48’s cooling system uses plastic components that can become brittle with age and heat cycling -the expansion tank and water pump are the most common failure points. Coolant loss can lead to overheating if not addressed promptly.

Tiered Cost Table

Preventative (Repair)

Dealer

Specialist

£600–£1,200

£400–£800

Catastrophic (Replacement)

Dealer

Specialist

£1,500–£3,000

£1,000–£2,000

Our Recommendation

On any B48‑powered G23 over 60,000 miles, have the cooling system inspected at every service -a £400–£800 preventative repair is far cheaper than the £1,000–£2,000 cooling system overhaul or engine replacement that follows an overheat event. The B48 is otherwise a robust engine.

Compare B48 cooling system repair quotes for your G23

02

48V

Mild‑Hybrid System Integration

Affected models:

G23 M440i xDrive, 420d, 430d, M440d xDrive (48V mild‑hybrid equipped models).

Typical failure mileage:

Unknown -new technology.

Root cause:

The 48V mild‑hybrid system (integrated starter‑generator, 48V battery) is relatively new across the BMW range. Early issues may include battery degradation, software integration problems, or starter‑generator failures. The system provides up to 11 hp of electric assistance.

Tiered Cost Table

Preventative (Repair)

Dealer

Specialist

£500–£1,500

£300–£1,000

Catastrophic (Replacement)

Dealer

Specialist

£2,000–£4,000

£1,500–£3,000

Our Recommendation

As a relatively new system, long‑term reliability data is limited. Ensure the 48V system is covered under warranty and have it inspected at major services. The mild‑hybrid system provides efficiency benefits and smoother stop‑start operation but adds complexity.

Compare G23 48V mild‑hybrid system checks

03

B47

Diesel DPF Clogging (urban use)

Affected models:

G23 420d (B47 diesel).

Typical failure mileage:

60,000–100,000 miles (urban driving).

Root cause:

Like all modern diesel engines, the B47's diesel particulate filter (DPF) can clog with soot if the car is predominantly used for short urban journeys where the DPF regeneration cycle cannot complete. The B47 is otherwise a robust and proven engine with an accessible front‑mounted timing chain.

Tiered Cost Table

Preventative (Repair)

Dealer

Specialist

£400–£800

£300–£600

Catastrophic (Replacement)

Dealer

Specialist

£1,500–£3,000

£1,000–£2,000

Our Recommendation

If you're buying a diesel G23 for urban use, ensure regular motorway runs to allow passive DPF regeneration. A £300–£600 DPF clean is far cheaper than the £1,000–£2,000 replacement that follows if ignored. The B47 is otherwise a dependable engine.

Compare B47 DPF service costs for your G23

04

Fabric

Soft Top Mechanism Wear

Affected models:

All G23 convertibles (2020–present).

Typical failure mileage:

60,000+ miles (age‑related).

Root cause:

Unlike the F33's folding hardtop, the G23 uses a fabric soft top -this is lighter and simpler but still has a hydraulic mechanism and microswitches that can wear with age. The fabric itself can also wear, particularly at crease points.

Tiered Cost Table

Preventative (Repair)

Dealer

Specialist

£500–£1,000

£300–£700

Catastrophic (Replacement)

Dealer

Specialist

£2,000–£4,000

£1,000–£2,500

Our Recommendation

Have the roof mechanism inspected at every major service on any G23 over 60,000 miles -a £300–£700 preventative service is dramatically cheaper than the £1,000–£2,500 full overhaul that follows if ignored. The fabric roof is simpler than the F33's hardtop but still requires maintenance.

Compare G23 roof mechanism repair quotes

G23 Engine Replacement Costs -By Engine and Condition

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

420iB48B20M0£1,200–£2,500£2,500–£4,500£4,000–£6,0008–12 hrs

430i / 430i xDriveB48B20O1£1,500–£2,800£2,800–£5,000£4,500–£6,5008–12 hrs

M440i xDriveB58B30B / B58B30TÜ1£2,500–£4,500£4,000–£7,000£6,000–£9,00010–14 hrs

420d / 420d xDriveB47D20B£1,200–£2,500£2,800–£4,500£4,000–£6,0008–12 hrs

430d / 430d xDriveB57D30A£2,500–£4,500£4,500–£7,500£6,500–£9,50010–14 hrs

M440d xDriveB57D30B£3,000–£5,000£5,000–£8,000£7,500–£10,50010–14 hrs

Core Variants

Diesel & Petrol Lineup

Diesel Variants

420d420d xDrive430d430d xDriveM440d xDrive

Petrol Variants

420i430i430i xDriveM440i xDrive

Scope note: All variants listed are G23 convertible only. The 420i uses the B48B20M0 (184 PS). The 430i uses the B48B20O1 (258 PS). The M440i xDrive uses the B58B30B (pre‑LCI, 382 PS) or B58B30TÜ1 (LCI, 382 PS). The 420d uses the B47D20B (190 PS). The 430d uses the B57D30A (282 PS). The M440d xDrive uses the B57D30B (340 PS). All diesel engines feature 48V mild‑hybrid technology. The 420i, 430i, 420d, 430d and M440d come standard with rear‑wheel drive but can be configured with xDrive; the M440i comes with xDrive only.

Diesel & Petrol Lineup

Diesel Variants

420d420d xDrive430d430d xDriveM440d xDrive

Petrol Variants

420i430i430i xDriveM440i xDrive

Scope note: All variants listed are G23 convertible only. The 420i uses the B48B20M0 (184 PS). The 430i uses the B48B20O1 (258 PS). The M440i xDrive uses the B58B30B (pre‑LCI, 382 PS) or B58B30TÜ1 (LCI, 382 PS). The 420d uses the B47D20B (190 PS). The 430d uses the B57D30A (282 PS). The M440d xDrive uses the B57D30B (340 PS). All diesel engines feature 48V mild‑hybrid technology. The 420i, 430i, 420d, 430d and M440d come standard with rear‑wheel drive but can be configured with xDrive; the M440i comes with xDrive only.

Market Intelligence

Most Requested E90 Engines (2025)

1.1. B58B30 (540 enquiries [EM-VERIFIED])
2.2. B47D20B (930 enquiries [EM-VERIFIED])
3.3. B48B20O1 (pattern data)

Most Requested E90 Variants

1.1. M440i xDrive
2.2. 420d
3.3. 430i

Average E90 Replacement Cost

£3,500–£6,500 supply only [BMW-QUOTE]

Most Common E90 Failures

1.1. B48 coolant leaks (expansion tank/water pump)
2.2. 48V mild-hybrid system integration
3.3. B47 DPF clogging (urban use)

Live Feed

VehicleLocationIssueEnquiries

BMW M440i

G23 (B58)

London

Coolant system check

4

enquiries

BMW 420d

G23 (B47)

Manchester

DPF regeneration

3

enquiries

BMW 420i

G23 (B48)

Birmingham

Coolant leak

2

enquiries

Updated Monthly

FAQ

BMW 3 Series E90 rear three-quarter view

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covering every variant from 420i to M440d xDrive, with supply‑only or full supply & fit available nationwide.

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BMW 4 Series G23 Engines -The Complete UK Guide

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BMW 4 Series G23 -Overview

BMW 4 Series G23 -Overview

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BMW 4 Series G23 -Ownership Economics

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G23 Engine Replacement Costs -By Engine and Condition

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Diesel &amp; Petrol Lineup

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Why UK BMW 4 Series G23 Owners Trust bmwengines.uk

Why UK BMW 4 Series G23 Owners Trust bmwengines.uk

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