Mercedes-Benz B-Class MOT failure rate and common faults
71,029 Mercedes-Benz B-Class cars aged 3 to 20 took their MOT in 2025, and 27.4% failed at the first attempt. An average car of the same age failed 30.1% of the time, which makes the Mercedes-Benz B-Class 9% less likely to fail than the typical car on the road. Here is what fails, and which years to look for.
27.4%
failed first time
71,029 MOT tests in 2025
-9%
vs same age average
average car of this age mix: 30.1%
92 of 208
age adjusted rank
among cars; 1 fails least
98.0
dangerous defects per 1,000
same age average: 110.0
What fails on a Mercedes-Benz B-Class MOT
Failure items recorded per 1,000 tests, by part of the car, set against an average car with exactly the same spread of ages. A figure well above average is a weak spot worth checking before you buy.
The most common Mercedes-Benz B-Class MOT failures
The individual failure items testers recorded most often, per 1,000 tests.
| Failure item | Area | Per 1,000 tests |
|---|---|---|
| Coil spring: fractured or broken | Suspension | 41.3 |
| Linkage ball joint dust cover: ball joint dust cover no longer prevents the ingress of dirt | Suspension | 34.4 |
| Drive shafts: constant velocity boot split or insecure, no longer prevents the ingress of dirt | Body, chassis, exhaust and drive shafts | 25.2 |
| Malfunction indicator lamp: inoperative or indicates a malfunction | Engine, emissions and leaks | 24.9 |
| Registration plate lamp(s): inoperative in the case of a single lamp or all lamps | Lights and electrics | 22.6 |
| Ball joint excessively worn | Suspension | 22.5 |
| Tyres: has a cut in excess of the requirements deep enough to reach the ply or cords | Tyres | 20.7 |
| Tread depth below requirements of 1.6mm | Tyres | 19.1 |
| Brake pads: less than 1.5 mm thick | Brakes | 18.4 |
| Tyres: has ply or cords exposed | Tyres | 18.2 |
Mercedes-Benz B-Class MOT failure rate by year
Every car fails more often as it ages, so each registration year is compared with the average for all cars of the same age. Years with fewer than 500 tests are left out.
| First registered | Tests | Failed | Same age average | Average mileage |
|---|---|---|---|---|
| 2022 | 1,315 | 9.0% | 11.4% | 24,800 |
| 2021 | 1,814 | 8.3% | 12.8% | 28,300 |
| 2020 | 2,923 | 10.0% | 14.1% | 31,400 |
| 2019 | 4,304 | 10.8% | 16.5% | 35,800 |
| 2018 | 3,973 | 16.5% | 19.1% | 44,300 |
| 2017 | 5,693 | 19.6% | 21.8% | 54,100 |
| 2016 | 5,360 | 20.8% | 25.1% | 60,900 |
| 2015 | 5,678 | 23.4% | 28.1% | 69,300 |
| 2014 | 8,209 | 28.2% | 31.4% | 77,400 |
| 2013 | 7,004 | 28.9% | 34.3% | 83,000 |
| 2012 | 5,758 | 30.7% | 36.6% | 88,000 |
| 2011 | 3,391 | 41.2% | 38.8% | 85,600 |
| 2010 | 4,334 | 41.7% | 40.7% | 91,800 |
| 2009 | 4,019 | 41.8% | 41.8% | 98,000 |
| 2008 | 3,080 | 44.8% | 42.9% | 101,200 |
| 2007 | 2,234 | 44.4% | 42.7% | 101,000 |
| 2006 | 1,612 | 43.5% | 43.0% | 101,800 |
Advisories to look for in a Mercedes-Benz B-Class's MOT history
An advisory is a tester's warning that something is wearing but has not failed yet. These are the ones written most often on the Mercedes-Benz B-Class, per 1,000 tests. If the car you are looking at has one of these, ask whether it has been fixed since.
- Tread depth: worn close to legal limit/worn on edge231.9
- Tyres: slightly damaged/cracking or perishing143.6
- Brake discs: worn, pitted or scored, but not seriously weakened117.0
- Rigid brake pipes: corroded, covered in grease or other material111.9
- Brake pads: wearing thin91.2
- Brake discs: worn, but not excessively52.3
Checking a used Mercedes-Benz B-Class before you buy
Against cars of the same age, the Mercedes-Benz B-Class fails more often than average on seat belts and airbags. Start there.
Seat belts and airbags
Pull every seat belt out fully and let it retract, check each buckle latches, and make sure the airbag warning light goes out after starting.
Averages only take you so far. The specific car's MOT history shows whether it has already failed on any of these, how often advisories were ignored, and whether the mileage climbs steadily from test to test. Read our guide to reading a car's MOT history before you go to view it.
Fuel mix of the Mercedes-Benz B-Class cars tested: Diesel 63%, Petrol 36%. Average age at test 11.1 years, average recorded mileage 71,400.
Mercedes-Benz B-Class MOT questions
What is the Mercedes-Benz B-Class MOT failure rate?
27.4% of Mercedes-Benz B-Class cars failed their first MOT test of 2025, from 71,029 tests on vehicles aged 3 to 20. An average car with the same age mix failed 30.1% of the time, so the Mercedes-Benz B-Class was 9% less likely to fail.
What fails most often on a Mercedes-Benz B-Class MOT?
Lights and electrics caused the most failure items, at 139 per 1,000 tests. The single most common failure item was "Coil spring: fractured or broken", recorded 41.3 times per 1,000 tests.
Which Mercedes-Benz B-Class year has the best MOT record?
Measured against cars of the same age, 2021 registrations did best: 8.3% failed against an average of 12.8% for cars that age. Older cars always fail more often, so compare a year with its age group rather than with newer cars.
Does this tell me whether a particular Mercedes-Benz B-Class will pass?
No. These are averages across every Mercedes-Benz B-Class tested in 2025. The car in front of you has its own record: its full MOT history shows every pass, failure and advisory it has had, and it is free to view by registration.
Other Mercedes-Benz models
- Mercedes-Benz A-Class21.5% failed
- Mercedes-Benz C-Class24.8% failed
- Mercedes-Benz E-Class22.3% failed
- Mercedes-Benz GLA16.8% failed
- Mercedes-Benz GLC13.7% failed
- Mercedes-Benz Vito32.5% failed
Ranked close to the Mercedes-Benz B-Class
- Toyota Yarisrank 89
- Volvo XC90rank 90
- BMW X2rank 91
- Volkswagen Passatrank 93
How these figures are calculated
Source: DVSA Anonymised MOT tests and results, 2025 release. We count first tests of cars and small vans (class 4) aged 3 to 20, so a car that fails and is retested is counted once. A failure includes faults fixed and passed within the same visit. The same age average weights the national failure rate for each age by how many Mercedes-Benz B-Class cars of that age were tested, so a model is never penalised for having an older fleet. Make and model are as recorded at the test; trim levels are combined. Full method and rankings.
Contains public sector information licensed under the Open Government Licence v3.0.