2021 Mercedes-Benz B MOT pass rate: 93.6% (2,513 tests)
Is the 2021 B getting worse?
Pass rate of 2021-registered cars across recent test years:
| Test year | Pass rate | |
|---|---|---|
| 2024 | 93.5% +2.9 vs same-age |
|
| 2025 | 93.7% +3.6 vs same-age |
The raw rate normally falls as cars age. The “vs same-age” figure compares this cohort with all UK cars registered in the same year, so normal ageing is not mistaken for a bad model year.
What fails on a 2021 B
| # | System | Defects recorded | Share |
|---|---|---|---|
| 1 | Tyres | 144 | 61.0% |
| 2 | Visibility | 27 | 11.4% |
| 3 | Brakes | 22 | 9.3% |
| 4 | Lamps, reflectors and electrical equipment | 13 | 5.5% |
| 5 | Seat belts and supplementary restraint systems | 8 | 3.4% |
| 6 | Identification of the vehicle | 7 | 3.0% |
All B years compared
| Registration year | Tests | Pass rate | Vs same-age | Median mileage |
|---|---|---|---|---|
| 2019 | 10,587 | 91.7% | +3.3 pts | 26,583 |
| 2020 | 8,219 | 92.8% | +2.9 pts | 22,242 |
| 2021 (this page) | 2,513 | 93.6% | +3.2 pts | 21,581 |
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FAQs
Is a 2021 Mercedes-Benz B reliable?
2021-registered examples passed 93.6% of their MOT tests (2,513 tests, 2023–2025), +3.2 points versus all UK cars registered in the same year. At roughly 5 years old with a median 21,581 miles, condition now varies car by car — always check the individual MOT history.
What mileage is too high for a 2021 B?
The median tested example shows 21,581 miles. Anything far beyond that isn't automatically bad — a motorway-mile car with consistent service records often beats a low-mileage school-run car — but price accordingly and scrutinise the mileage trail for gaps or drops.
Source: DVSA Anonymised MOT tests and results, 2023–2025 extracts (96 million Class 4 initial tests; retests excluded). Only vehicles old enough for a routine first MOT are included. Age-adjusted figures compare the model-year cohort with all vehicles of the same registration year tested in the same calendar year. Contains public sector information licensed under OGL v3.0.