72.6%
Mercedes-Benz B-Class
Mercedes-Benz B-Class MOT pass rate and common problems
The Mercedes-Benz B-Class passed 72.6% of its initial MOT tests in 2025, in line with the 72.3% UK average. The item testers recorded most often was coil spring fractured or broken.
Checking a specific car? Its own results, advisories and recorded mileages are in a free MOT history check.
How the B-Class compares
Initial MOT tests in 2025, retests excluded. A car that failed and was repaired at the test station counts as a fail.
77.1%
Mercedes-Benz average
72.3%
UK average, all cars
The B-Class runs 4.4 points behind the Mercedes-Benz average. It is 25th of the 35 Mercedes-Benz models in the data. The average B-Class arrived at its test 11.1 years old with 71,392 miles recorded.
A pass rate records whether cars met the roadworthiness standard on test day. It is not a reliability score, and part of any gap reflects how old the tested cars were.
B-Class MOT pass rate by age
The same 2025 tests split by the car's age at test.
Mercedes-Benz B-Class cars aged 3 to 5 years passed 90.3% of MOT tests. For cars aged 11 years and over that fell to 63.6%, a drop of 26.7 percentage points.
| Age at test | Tests | Pass rate | vs UK average |
|---|---|---|---|
| 3 to 5 years | 8,147 | 90.3% | 18 pts above |
| 6 to 10 years | 25,943 | 78.8% | 6.5 pts above |
| 11 years and over | 35,973 | 63.6% | 8.7 pts below |
That is a steep decline with age, so the headline rate flatters older examples. The UK average of 72.3% covers cars of every age, so compare like with like.
Where B-Class failures cluster
Every failure item recorded on Mercedes-Benz B-Class cars in 2025, grouped into the DVSA's test areas.
Lamps, reflectors and electrical equipment and suspension together account for 45.3% of recorded failure items. These are recorded failures across the model, not faults every car has.
The 10 most common B-Class MOT failures
Specific items recorded on Mercedes-Benz B-Class cars that failed their 2025 MOT, as a share of all recorded failure items.
Together these 10 items make up 41.1% of everything testers recorded against failed Mercedes-Benz B-Class cars. The rest is spread across many smaller items, and one failed test often records several at once.
What to look at on a B-Class
The recorded failures above, grouped by area, biggest first.
1
Suspension
Recorded most often: coil spring fractured or broken, linkage ball joint dust cover ball joint dust cover no longer prevents the ingress of dirt and ball joint excessively worn. 16.3% of failure items.
2
Tyres
Recorded most often: condition has a cut in excess of the requirements deep enough to reach the ply or cords, tread depth below requirements of 1.6mm and condition has ply or cords exposed. 9.7% of failure items.
3
Body, chassis, structure
Recorded most often: joints constant velocity boot split or insecure, no longer prevents the ingress of dirt. 4.2% of failure items.
4
Noise, emissions and leaks
Recorded most often: malfunction indicator lamp inoperative or indicates a malfunction. 4.1% of failure items.
The car's own MOT history matters more than any model average. A free MOT history check shows whether a specific B-Class has failed on these items before, or had them noted as advisories. Buying one? See the used Mercedes-Benz B-Class buying guide.
Already found one?
Check its finance, write-off, theft, mileage and keeper history with a £15 vehicle history report.
Mercedes-Benz B-Class MOT FAQs
What is the Mercedes-Benz B-Class MOT pass rate?
72.6% of Mercedes-Benz B-Class cars passed their initial MOT first time in 2025, from 71,070 tests. That is in line with the 72.3% average for all cars, and ranks 299th of 575 models.
What does a Mercedes-Benz B-Class most commonly fail its MOT on?
The item testers recorded most often on Mercedes-Benz B-Class cars failing their 2025 MOT was coil spring fractured or broken, on 6.8% of failure items. Next were linkage ball joint dust cover ball joint dust cover no longer prevents the ingress of dirt (5.7%) and joints constant velocity boot split or insecure, no longer prevents the ingress of dirt (4.2%).
Which area causes the most Mercedes-Benz B-Class MOT failures?
Across every recorded failure item, the largest area was lamps, reflectors and electrical equipment at 22.8%, followed by suspension at 22.4%.
Do older Mercedes-Benz B-Class cars fail their MOT more often?
Mercedes-Benz B-Class cars aged 3 to 5 years passed 90.3% of MOT tests in 2025, against 63.6% for cars aged 11 years and over.
Does this mean every Mercedes-Benz B-Class has these problems?
No. These are the items testers recorded across every Mercedes-Benz B-Class that failed in 2025. They show where the model most often needs attention, not the condition of any individual car.
How do I see a specific Mercedes-Benz B-Class's MOT history?
Enter its registration on the free Carpeep MOT history check to see that car's own test results, failures, advisories and recorded mileages.
MOT figures are aggregated from the DVSA MOT Anonymised data set for 2025: class 4 initial tests, retests excluded, with failure items from failed tests (advisories and minor defects excluded), licensed under the Open Government Licence v3.0. MOT results describe roadworthiness at test, not mechanical reliability.