Mercedes-Benz B-Class MOT pass rate & common failures

At a glance

Pass rate, adjusted for age and mileage

The B-Class is 1.0 percentage points above the national pass rate once age and mileage are accounted for, which is above average. The unadjusted figure is 72.6%; the difference is what the age and mileage of this model’s fleet was hiding.

DVSA recorded wording

Most common failure items

Share of failed Mercedes-Benz B-Class tests in which each item was recorded. One failed test often lists several items, so these do not sum to 100%.

1. 1.A spring or spring component fractured or seriously weakened18.1%

   2,917 occurrencesRoad spring broken or fractured explained

2. 2.A suspension joint dust cover missing or no longer prevents the ingress of dirt etc15.0%

   2,415 occurrencesSuspension joint dust cover missing or split explained

3. 3.A transmission shaft constant velocity joint boot missing or no longer prevents the ingress of dirt etc10.9%

   1,760 occurrencesDriveshaft CV joint gaiter split or missing explained

4. 4.A tyre seriously damaged9.1%

   1,466 occurrencesTyre damaged or deteriorated explained

5. 5.A suspension pin, bush or joint excessively worn8.7%

   1,395 occurrencesSuspension arm bush worn explained

6. 6.A rear registration plate lamp or light source missing or inoperative in the case of a single lamp or all lamps8.6%

   1,391 occurrencesLamp not working explained

7. 7.A tyre cords visible or damaged8.0%

   1,284 occurrencesTyre ply or cord exposed, or the casing separating explained

8. 8.Tyre tread depth not in accordance with the requirements7.9%

   1,266 occurrencesTyre worn close to the legal limit explained

9. 9.A brake lining or pad worn below 1.5mm7.8%

   1,259 occurrencesBrake drum or shoe worn or contaminated explained

10. 10.Brake pipe damaged or excessively corroded7.2%

    1,163 occurrencesBrake pipe corroded explained

Warnings without a failure

Most common advisories

Share of all Mercedes-Benz B-Class tests carrying each advisory. The denominator differs from the failure list above because an advisory can be issued on a car that passed.

1. 1.Tyre tread depth not in accordance with the requirements20.4%

   14,441 testsTyre worn close to the legal limit explained

2. 2.A tyre seriously damaged14.4%

   10,223 testsTyre damaged or deteriorated explained

3. 3.Brake disc or drum excessively weakened, insecure or fractured11.8%

   8,324 testsBrake disc worn, pitted or scored explained

4. 4.Brake pipe damaged or excessively corroded11.2%

   7,940 testsBrake pipe corroded explained

5. 5.A brake lining or pad worn below 1.5mm9.2%

   6,506 testsBrake drum or shoe worn or contaminated explained

6. 6.Brake disc or drum significantly and obviously worn5.3%

   3,740 testsBrake disc worn, pitted or scored explained

7. 7.A spring or spring component fractured or seriously weakened3.9%

   2,784 testsRoad spring broken or fractured explained

8. 8.A suspension pin, bush or joint excessively worn3.2%

   2,231 testsSuspension arm bush worn explained

How wear changes the picture

Pass rate by vehicle age

Bands holding too few tests to be meaningful are omitted rather than shown as a rate.

What gets tested

The B-Class fleet

Average mileage recorded at test

71,375

Across examples of every age, so this is a description of the fleet rather than an annual figure.

Fuel mix of tested cars

Diesel63.3%

Petrol35.4%

Hybrid0.8%

Electric0.6%

Compare within the range

Other Mercedes-Benz models

• Mercedes-Benz A-Class — 73.3% adjusted
• Mercedes-Benz C-Class — 77.0% adjusted
• Mercedes-Benz E-Class — 78.5% adjusted
• Mercedes-Benz GLA — 82.3% adjusted
• Mercedes-Benz Vito — 71.0% adjusted
• Mercedes-Benz GLC — 85.9% adjusted
• All Mercedes-Benz models →

Similar test volumes

Compare against other makes

• Suzuki Vitara — 76.2% adjusted, ranked 94
• Renault Kadjar — 74.0% adjusted, ranked 121
• Nissan Navara — 68.6% adjusted, ranked 186
• Mazda CX-5 — 78.5% adjusted, ranked 71

Common questions

Is the Mercedes-Benz B-Class reliable?

On MOT evidence the Mercedes-Benz B-Class is above average. It passes 73.3% of tests once age and mileage are accounted for, against a national average of 72.3%, which ranks it 130 of 262 models with enough data for a fair comparison. This measures how often the car meets the MOT standard, not how often it breaks down or what a repair costs.

What is the most common MOT failure on a Mercedes-Benz B-Class?

The item recorded most often is "A spring or spring component fractured or seriously weakened", which appears in 18.1% of failed Mercedes-Benz B-Class tests. Because one failed test can list several items, these shares do not add up to 100%.

What do testers most often warn about on a Mercedes-Benz B-Class?

The most common advisory is "Tyre tread depth not in accordance with the requirements", noted on 20.4% of all Mercedes-Benz B-Class tests. An advisory is not a failure: it flags something that will likely need attention before the next test.

What mileage does a Mercedes-Benz B-Class usually have at its MOT?

The average odometer reading recorded at test is 71,375 miles. This is the mileage across all tested examples of every age, not an annual figure, so treat it as a description of the fleet rather than a target for one car.

Does a Mercedes-Benz B-Class get harder to pass as it ages?

Yes. At 3 to 5 years old, 90.8% of Mercedes-Benz B-Class tests pass. By fifteen years or more, that falls to 57.0%. Nearly every model follows this pattern, which is why comparing raw pass rates between models is misleading unless age is accounted for.

Are most Mercedes-Benz B-Class models petrol or diesel?

Of the Mercedes-Benz B-Class cars tested, 63% are diesel, 35% are petrol, 1% are hybrid. Fuel type affects which items tend to fail, particularly emissions and exhaust components.

How this was worked out

Method and limits

Figures come from the DVSA anonymised MOT testing dataset, published under the Open Government Licence. Only class 4 initial tests are counted: retests are excluded so a car appears once, and abandoned tests are excluded entirely. The adjusted rate is directly standardised across twenty-five age and mileage bands and reweighted onto the national distribution, so this model is compared against cars that have lived a similar life rather than against a younger or lighter-used fleet.

An MOT measures whether a car met a legal standard on the day. It is not a breakdown record, a service history or a running-cost estimate, and a pass rate is a property of a fleet rather than a prediction about one car.

Further reading

Make sense of the numbers

• How to judge reliability from evidence rather than reputation
• What counts as high or low mileage for a car’s age
• The most common MOT failures and how to avoid them
• What to check before buying a used Mercedes-Benz