BMW 420i — MOT pass rate & failures
The BMW 420i recorded a 89.3% MOT pass rate across 118,628 tests in this dataset (model years 2013–2024), with tyres, lighting & signalling and brakes its most common failure areas. Its 10.7% fail rate is lower than the 11.8% average across all BMW 4 Series versions.
How it compares
By model year
| Year | Tests | Pass rate | Fail rate |
|---|---|---|---|
| 2013 | 517 | 85.1% | 14.9% |
| 2014 | 8,077 | 85.9% | 14.1% |
| 2015 | 12,593 | 87.6% | 12.4% |
| 2016 | 14,130 | 88.8% | 11.2% |
| 2017 | 14,558 | 90.0% | 10.0% |
| 2018 | 28,062 | 89.9% | 10.1% |
| 2019 | 20,424 | 89.5% | 10.4% |
| 2020 | 8,496 | 91.0% | 9.0% |
| 2021 | 7,549 | 90.9% | 9.1% |
| 2022 | 4,002 | 91.0% | 8.9% |
| 2023 | 217 | 93.1% | 6.9% |
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Tyres | 6.8% | 8,117 |
| 2 | Lighting & signalling | 2.1% | 2,479 |
| 3 | Brakes | 1.8% | 2,099 |
| 4 | Visibility | 1.4% | 1,686 |
| 5 | Suspension | 0.7% | 858 |
| 6 | Road wheels | 0.5% | 617 |
| 7 | Other defects | 0.4% | 414 |
| 8 | Emissions & environmental | 0.3% | 376 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Tread depth | 2,646 |
| 2 | Brake pads | 1,857 |
| 3 | Headlamp aim | 1,612 |
| 4 | Washers | 1,255 |
| 5 | Registration plates | 645 |
| 6 | Wipers | 602 |
Top advisory categories
Advisories aren't failures, but they flag work likely needed soon — useful when budgeting.
| # | Category | % of tests with advisory | Tests |
|---|---|---|---|
| 1 | Tyres | 20.0% | 23,683 |
| 2 | Brakes | 12.8% | 15,175 |
| 3 | Other defects | 6.0% | 7,138 |
| 4 | Suspension | 2.7% | 3,204 |
| 5 | Visibility | 2.3% | 2,671 |
| 6 | Emissions & environmental | 1.0% | 1,222 |
Failure rate by mileage
Higher-mileage cars tend to fail more — often the most useful guide to real condition.
| Mileage band | Tests | Fail rate |
|---|---|---|
| 0-30k | 41,830 | 7.6% |
| 30-60k | 54,247 | 11.3% |
| 60-90k | 17,849 | 14.0% |
| 90-120k | 3,831 | 16.9% |
| 120-150k | 706 | 18.8% |
| 150k+ | 163 | 20.9% |
Failure rate by age
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 15,953 | 9.4% |
| 2022 | 21,085 | 10.1% |
| 2023 | 23,621 | 10.5% |
| 2024 | 27,092 | 11.2% |
| 2025 | 30,877 | 11.3% |
What to check before buying a BMW 420i
Focus on the areas it most often fails on — and remember MOT data covers testable defects only, not engine or gearbox health.
- Tyres (6.8% of tests): Usually a quick, known-cost fix, but check tread, age and uneven wear (which can hint at alignment or suspension issues). Typical repair: £50–£120 per tyre.
- Lighting & signalling (2.1% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Brakes (1.8% of tests): Pads/discs are routine wear; binding, imbalance or corroded pipes are more serious — test for pulling under braking. Typical repair: £100–£350 per axle.
Repair costs are rough UK ballpark ranges to set expectations, not quotes — actual prices vary widely by car, parts and garage.
Frequently asked questions
How reliable is the BMW 420i at MOT time?
89.3% of the 118,628 BMW 420i MOT tests in this dataset passed — a 10.7% fail rate, better than the 11.8% average across all 4 Series versions.
What is the most common MOT failure on a BMW 420i?
Tyres, recorded in 6.8% of tests, followed by lighting & signalling (2.1%).
Does the 420i get worse with mileage?
Its MOT fail rate rises from 7.6% in the 0-30k band to 20.9% in the 150k+ band.
Methodology & source. Based on 118,628 MOT tests. Dataset: DVSA MOT testing data (2021,2022,2023,2024,2025). Data last updated 2026-07-06. Figures reflect MOT-testable defects only — read the methodology for how these are calculated and what they don't measure.