In 2025, 68,778 Mercedes-Benz B-Class cars had a regular MOT in Great Britain. 72% passed first time, compared with 69% for all cars of the same ages, which makes the B-Class about average. Adjusted for age, it ranks 91 of the 217 most-tested car models.
That comparison matters: older cars fail more often, so a raw pass rate flatters models that are mostly young. We compare each model against every car on the road at the same age.
Pass rate by age
At 3 years old, 93% of B-Classs passed first time (all cars that age: 88%). By 20 years, that figure is 55% (all cars: 58%). It starts out ahead of the average car but falls behind from around 20 years, which is worth knowing if you are buying an older one.
Mercedes-Benz B-Class All cars of that age
| Age | Tests | B-Class passed first time | All cars | Typical mileage |
|---|---|---|---|---|
| 3 years | 232 | 93% | 88% | 23,450.6810344828 |
| 4 years | 1,272 | 92% | 87% | 27,368.7523584906 |
| 5 years | 2,752 | 90% | 86% | 31,340.6529796512 |
| 6 years | 4,185 | 89% | 84% | 35,815.7283154122 |
| 7 years | 3,963 | 83% | 81% | 44,244.0847842544 |
| 8 years | 5,686 | 80% | 78% | 54,061.1514245515 |
| 9 years | 5,349 | 79% | 75% | 60,902.5133669845 |
| 10 years | 5,656 | 77% | 72% | 69,418.6166902405 |
| 11 years | 8,183 | 72% | 69% | 77,485.7949407308 |
| 12 years | 6,973 | 71% | 66% | 83,070.8366556719 |
| 13 years | 5,668 | 69% | 63% | 88,128.0338743825 |
| 14 years | 3,365 | 59% | 61% | 85,570.2852897474 |
| 15 years | 4,282 | 58% | 59% | 91,858.1069593648 |
| 16 years | 3,973 | 58% | 58% | 97,873.6894034734 |
| 17 years | 3,067 | 55% | 57% | 101,299.047929573 |
| 18 years | 2,224 | 56% | 57% | 101,052.380395683 |
| 19 years | 1,597 | 56% | 57% | 101,928 |
| 20 years | 325 | 55% | 58% | 104,577.193846154 |
What fails most on a Mercedes-Benz B-Class
The area that lets the B-Class down most, relative to other cars, is seat belts and airbags: 1.5% of tests failed on it, 4.4 times the rate for the average car.
Share of B-Class tests failing on this area Average car
The six most common failure items
| Failure item | Area | Share of tests |
|---|---|---|
| A suspension joint dust cover missing or no longer prevents the ingress of dirt etc | Suspension | 5.0% |
| A spring or spring component fractured or seriously weakened | Suspension | 4.2% |
| A tyre seriously damaged | Tyres | 4.0% |
| The aim of a headlamp is not within limits laid down in the requirements | Lights and electrics | 3.5% |
| A suspension pin, bush or joint excessively worn | Suspension | 2.9% |
| A transmission shaft constant velocity joint boot missing or no longer prevents the ingress of dirt etc | Body and structure | 2.6% |
What to check when buying a used B-Class
Based on where the B-Class fails more often than other cars, these are the checks worth making before you buy:
- Seat belts and airbags: Pull every belt out fully and let it retract, check the buckles latch, and make sure the airbag light goes out after starting. More
- Tyres: Check tread across the whole width (uneven wear hints at alignment or suspension faults), and look for cuts, bulges and mismatched brands. Repair guide
- Suspension: Listen for knocks over speed bumps, look for leaking shock absorbers, and check the car sits level. Ask whether springs, bushes or drop links have been replaced. Repair guide
Then check the individual car: its own MOT history will show whether it follows the pattern. A car with repeated advisories in the same weak area is more likely to fail its next test.
Check a specific B-Class
Enter the registration to see its full MOT history, mileage record and reliability score, compared with these figures.
Check a B-ClassFrequently asked questions
What is the MOT pass rate for a Mercedes-Benz B-Class?
In 2025, 72% of Mercedes-Benz B-Class cars passed their MOT first time, across 68,778 tests. Cars of the same ages averaged 69%.
What do Mercedes-Benz B-Class cars most often fail their MOT on?
The most common failure items were: a suspension joint dust cover missing or no longer prevents the ingress of dirt etc (5.0% of tests); a spring or spring component fractured or seriously weakened (4.2% of tests); a tyre seriously damaged (4.0% of tests).
Other Mercedes-Benz models
Mercedes-Benz C-Class (74%), Mercedes-Benz A-Class (77%), Mercedes-Benz E-Class (77%), Mercedes-Benz Vito (67%), Mercedes-Benz Glc (85%), Mercedes-Benz Gla (80%). All Mercedes-Benz models
Source: DVSA anonymised MOT tests and results, 2025 (class 4 normal tests; first-time pass means passed with no faults fixed at the test). Contains public sector information licensed under the Open Government Licence v3.0.