BMW 1 Series F21 Engines -The Complete UK Guide
Every engine fitted to the 1 Series F21 three‑door -from the entry‑level 114i to the fire‑breathing M135i and M140i six‑cylinders, and the full range of N47 and B47 diesel fours that define UK ownership. Real UK costs, honest failure data, and the 2015 facelift engine refresh that brought BMW’s modular B‑series engines to the range. Backed by 344+ real UK F20/F21 enquiries in 2025 [BMW‑VERIFIED].
Explore F21 Engines
BMW 1 Series F21 Engine Codes -The Complete Database
Every engine fitted to the F21 three‑door -from the pre‑LCI N‑series engines to the post‑2015 B‑series modular family that brought three‑cylinder power to the range.
Overview
BMW 1 Series F21 -Overview
The BMW 1 Series F21 is the three‑door hatchback variant of the second‑generation 1 Series, produced from September 2011 to May 2019.
Built on BMW’s L7 platform and featuring rear‑wheel drive for most models (with xDrive all‑wheel drive available as an option), the F21 offered a wide range of turbocharged petrol and diesel engines. A significant 2015 facelift (LCI) brought BMW’s modular B‑series engine family to the range, replacing the N‑series engines with more efficient three‑ and four‑cylinder units. The range was topped by the M135i and later M140i, featuring 3.0‑litre six‑cylinder turbocharged engines that made the F21 one of the most engaging hot hatchbacks of its era.
Key Facts
Platform
BMW L7
Predecessor
BMW 1 Series E87/E81
Successor
BMW 1 Series F40
Sibling body styles in this generation
F20 (5‑door hatchback)
Market Intelligence
The BMW 1 Series F20/F21 generated 344 real UK engine enquiries in 2025 [EM‑VERIFIED], concentrated on the N47 diesel fours as the parc exits affordable‑warranty age and timing‑chain concerns come to the fore.
Best & Worst Engines
Best Diesel Overall
B47D20A (post‑2015, 118d/120d)
““The B47 is BMW’s modular diesel four -front‑mounted timing chain, far more accessible than the N47’s rear‑mounted design, and generally regarded as a strong and dependable engine capable of high mileage if properly maintained.” Who it’s for: buyers who want diesel economy without the N47’s timing‑chain anxiety.”
Who it's for:
Best Petrol Overall
B58B30A (M140i, 2016–2019)
““The B58 is BMW’s modular straight‑six masterpiece -340 bhp, silky smooth, and chain‑driven with a robust bottom end. It’s the engine that made the M140i the hot hatch benchmark. The most reliable engine in the F21 range.” Who it’s for: buyers who want six‑cylinder performance without the N55’s fuel‑pump anxieties.”
Who it's for:
Highest Risk
N47D20C (pre‑2015, 116d/118d/120d)
““The rear‑mounted timing chain is the defining risk of the pre‑LCI diesel four -cold‑start rattle is the warning, and a snapped chain means full replacement. The N47 is the single biggest ownership risk on the F21.” Who it’s for: only buyers with documented chain‑replacement history.”
Who it's for:
Most Expensive Failure
N47D20D / N47S1 (125d, pre‑2015)
““The high‑output N47 in the 125d carries the same rear‑chain risk as the lower‑output variants, but with more power and higher stresses. A snapped chain in a 125d means the same £3,500–£6,000 replacement.” Who it’s for: 125d buyers with deep pockets and full service history.”
Who it's for:
Best Value
B47D20A (post‑2015, 118d/120d)
““The B47 is the N47’s successor -front‑mounted chain, better oil supply, and significantly lower risk of catastrophic failure. It’s the diesel four you can buy without anxiety.” Who it’s for: buyers who want modern diesel efficiency without the N47’s caveats.”
Who it's for:
Most Overlooked
B48B20A (120i, 2016–2019)
““The B48 is the four‑cylinder petrol that replaced the N13 -184 bhp, chain‑driven, and significantly more reliable than the N13 it replaced. It’s the sweet spot of the petrol range.” Who it’s for: buyers who want petrol refinement without the M140i’s running costs.”
Who it's for:
BMW 1 Series F21 -Ownership Economics
The F21 rule
A £3,200–£5,500 N47 recon against a £4,000–£12,000 F21 sits at 27–137% of the car’s value. On a sub‑£5,000 F21, that brushes our 70% BMW threshold -we’ll honestly tell you to walk away. Against a well‑kept £10,000+ example, the same recon drops to a routine 32–55% -a repair decision, not a financial one. Value the car first.
Common Problems
F21 Engine Replacement Costs -By Engine and Condition
No Generation variance from the Model Page’s baseline figures -F21 shares its engine‑bay layout with the F20 5‑door, so costs are inherited directly per the Authority Model, with no divergence note required. N47 and B47 costs are carried forward from the Model Page’s existing cost tables.
Core Variants
Diesel & Petrol Lineup
Scope note: All variants listed are F21 3‑door hatchback only. The 125i was offered with the N20B20 engine producing 218 bhp (pre‑LCI) and later 238 bhp. The M135i (pre‑LCI) used the N55B30A six‑cylinder producing 326 bhp. The M140i (LCI) used the B58B30A producing 340 bhp. The 120i was offered with the N13 (pre‑LCI, 177 bhp) and later the B48 (LCI, 184 bhp). The 125d was offered with the N47D20D (pre‑LCI, 218 bhp) and later the B47D20B (LCI, 224 bhp). The 114d and 116d were offered with the N47D16A/N47D20C (pre‑LCI) and later the B37D15A (LCI).
Market Intelligence
Most Requested E90 Engines (2025)
- 1.1. N47D20C (1,450 JLR‑wide enquiries [EM‑VERIFIED])
- 2.2. B47D20A (930 JLR‑wide [EM‑VERIFIED])
- 3.3. N55B30A (M135i pattern data)
Most Requested E90 Variants
- 1.1. 120d
- 2.2. 118d
- 3.3. M135i
Average E90 Replacement Cost
£2,800–£5,500 supply only [BMW‑QUOTE]
Most Common E90 Failures
- 1.1. N47 timing chain stretch
- 2.2. N13 timing chain tensioner wear
- 3.3. N55 HPFP / injector failure
BMW 120d
F21 (N47)
6
enquiries
BMW M135i
F21 (N55)
4
enquiries
BMW 118i
F21 (N13)
3
enquiries
FAQ
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