BMW 4 Series F33 Engines -The Complete UK Guide
Every engine fitted to the F33 convertible -from the N47 diesel to the N55 straight-six and the B58 that redefined the range. Real UK replacement costs, honest failure data, and the N20 timing-chain risk that still haunts early four-cylinder petrol cars. Backed by 256+ real UK F33 enquiries in 2025 [BMW-VERIFIED].
Explore F33 Engines
BMW 4 Series F33 Engine Codes -The Complete Database
Every engine fitted to the F33 convertible -from the pre‑LCI N‑series units to the post‑LCI B‑series replacements that improved reliability and performance.
Overview
BMW 4 Series F33 -Overview
The F33 is the convertible body of BMW's first-generation 4 Series, launched in March 2014 as the direct successor to the E93 3 Series Convertible.
It introduced a new naming convention -the 4 Series replacing the 3 Series coupé and convertible -while retaining the E93's three-piece retractable metal hardtop. The engine range spans from four-cylinder diesels and petrols to the range-topping six-cylinder N55 and B58 units. A 2017 Life Cycle Impulse (LCI) brought significant mechanical updates: the N20 four-cylinder petrol was replaced by the B48, the N55 by the B58, and the N47 diesel was superseded by the B47.
Key Facts
Platform
BMW F3x (shared with F32 Coupé, F36 Gran Coupé, F30 3 Series)
Predecessor
BMW 3 Series E93 Convertible (2007–2013)
Successor
BMW 4 Series G23 Convertible (2020–present)
Sibling body styles in this generation
F32 Coupé (2-door), F36 Gran Coupé (4-door liftback)
Market Intelligence
The F33 convertible generated 256 real UK engine enquiries in 2025 [BMW-VERIFIED], concentrated on the N20 four-cylinder petrol and N47 diesel units as these cars age out of warranty and timing-chain issues become a significant concern.
Best & Worst Engines
Best Diesel Overall
B47D20 (2.0-litre diesel, 420d, 2015–2020)
“The B47 replaced the N47 in the 420d and brought the timing chain to the front of the engine -a significant reliability improvement. With 190 bhp and 400 Nm of torque, it delivers strong performance and genuine 50+ MPG economy. It's the diesel to have in an F33.”
Who it's for: Buyers who need diesel economy and torque without the N47's timing-chain anxiety.
Best Petrol Overall
B58B30 (3.0-litre straight-six, 440i, 2016–2020)
“The B58 is BMW's modular straight-six and arguably the best engine ever fitted to a 4 Series. 326–335 bhp, 450 Nm of torque, and a reputation for reliability that rivals Toyota's standards -it's so good Toyota uses it in the Supra. It transforms the F33 into a genuine grand tourer.”
Who it's for: Enthusiasts who want the ultimate F33 engine and are willing to pay for it.
Highest Risk
N20B20 (2.0-litre petrol, 420i/428i/430i, 2014–2017)
“The N20 four-cylinder petrol suffers from timing-chain guide failure -plastic guides become brittle and break, leading to catastrophic engine failure. The chain is located at the rear of the engine, making replacement labour-intensive. Pre-2015 cars are the highest risk.”
Who it's for: Buyers who want an entry-level F33 and have budgeted for timing-chain replacement.
Most Expensive Failure
N20 Timing Chain & Guide Failure
“When the N20's timing chain guides fail, the chain can snap, destroying the engine. A full replacement of chain, guides and tensioner costs £1,500–£2,500 at a specialist; a snapped chain means a full engine replacement at £3,800–£6,000. It's the most expensive non-catastrophic failure in the F33 range.”
Who it's for: Buyers who want to pay for preventative maintenance rather than a replacement.
Best Value
420d with B47 (post-2015)
“The B47-powered 420d delivers 190 bhp, 400 Nm, and 50+ MPG economy -the best all-rounder in the F33 range. It's more reliable than the N47 it replaced, more economical than the six-cylinder cars, and holds its value well. The sweet spot in the range.”
Who it's for: Buyers who want performance, economy and value in one package.
Most Overlooked
430i with B48 (post-LCI, 2017–2020)
“The B48-powered 430i is often overshadowed by the 440i's six-cylinder power and the 420d's economy. But with 252 bhp and a closed-deck design that improves reliability, it's the Goldilocks engine -enough power to be exciting, enough economy to be sensible, and more reliable than the N20 it replaced.”
Who it's for: Buyers who want the best balance of performance, reliability and running costs.
BMW 4 Series F33 -Ownership Economics
The F33 rule
A £3,800–£6,000 N20 recon against a £10,000–£25,000 F33 sits at 15–60% of the car's value -a significant decision. On a sub-£10,000 high-mileage example, that brushes our 70% BMW threshold -we'll honestly tell you to walk away. Against a well-kept £18,000+ example, the same recon drops to a routine 21–33% -a repair decision, not a financial one. The convertible roof mechanism also adds a unique cost dimension to F33 ownership.
Key Takeaways
Which F33 Costs Least To Own?
430i (B48) -reliable four-cylinder petrol, simpler than six-cylinder, no DPF.
Which F33 Costs Most To Own?
435i (N55) -HPFP, VANOS and oil leaks add up; six-cylinder fuel consumption.
Which F33 Is Best Value?
440i (B58) -the best engine in the range, strongest residuals, the one enthusiasts want.
Common Problems
F33 Engine Replacement Costs -By Engine and Condition
Core Variants
Diesel & Petrol Lineup
Scope note: All variants listed are F33 convertible only -the two-door, four-seat convertible produced from 2014 to 2020. F32 Coupé and F36 Gran Coupé are covered on their own Generation Pages, as fitment and labour access vary by body style. M4 (F83) is covered separately.
Market Intelligence
Most Requested E90 Engines (2025)
- 1.1. N20B20 (420i/428i/430i, 2.0-litre petrol)
- 2.2. N47D20C / B47D20 (420d, 2.0-litre diesel)
- 3.3. B58B30 (440i, 3.0-litre straight-six) -based on UK specialist enquiry patterns [PATTERN DATA]
Most Requested E90 Variants
- 1.1. BMW 420d
- 2.2. BMW 430i
- 3.3. BMW 440i -based on model-level request data [BMW‑VERIFIED]
Average E90 Replacement Cost
£3,200–£7,500 reconditioned, supply only [BMW‑QUOTE]
Most Common E90 Failures
- 1.1. N20 timing chain guide failure
- 2.2. N47 diesel timing chain stretch
- 3.3. F33 retractable hardtop mechanism issues
BMW 430i
F33
6
enquiries
BMW 420d
F33
4
enquiries
BMW 440i
F33
3
enquiries
FAQ
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