Diesel Mercedes-Benz B-Class: MOT pass rate

75.1% of diesel Mercedes-Benz B-Class pass the MOT first time, measured across 43,228 DVSA tests on that fuel type alone. Average mileage at test was 78,400.

Diesel against the other Mercedes-Benz B-Class versions

Why the fuel type changes the number

Diesels carry DPFs, EGR valves and stricter smoke limits, so emissions and exhaust faults account for failures petrol cars never see.

On the Mercedes-Benz B-Class specifically, electric is the strongest at 84.5%, and this diesel version sits 0.1 points below the 75.2% model average.

What it means if you are buying one

There is little to choose between fuel types on this model, so decide on running costs and mileage rather than MOT record. Buying a damaged one? run it through the analyzer, check the exact car, decode the VIN and check the mileage before you bid.

Mileage is part of the answer

The average diesel Mercedes-Benz B-Class had covered 78,400 miles at test, against 71,194 for the petrol and 45,186 for the electric. That is a shade above the middle of the range, still ordinary wear rather than a red flag, but worth checking against the service book for the car's age.

Fuel type and mileage are tangled together: diesels are usually bought by higher-mileage drivers, so some of any gap between fuels is the miles rather than the engine. The per-year figures on the Mercedes-Benz B-Class page separate age from fuel if you want to isolate one.

Most common MOT failures on a diesel Mercedes-Benz B-Class

1. A rear registration plate lamp or light source missing or inoperative in the case of a single lamp or all lamps, 2.8% of tests (3.09x the national rate for this defect)
2. A suspension joint dust cover missing or no longer prevents the ingress of dirt etc, 5.1% of tests (2.76x the national rate for this defect)
3. A direction indicator lamp missing, inoperative or in the case of a multiple light source more than 1/2 not functioning, 1.5% of tests (2.36x the national rate for this defect)
4. Brake pipe damaged or excessively corroded, 2.1% of tests (1.99x the national rate for this defect)
5. A spring or spring component fractured or seriously weakened, 4.3% of tests (1.88x the national rate for this defect)
6. A tyre seriously damaged, 4.5% of tests (1.6x the national rate for this defect)
7. Engine MIL illuminated indicating a malfunction, 2% of tests (1.6x the national rate for this defect)
8. A tyre cords visible or damaged, 2.3% of tests (1.35x the national rate for this defect)
9. A transmission shaft constant velocity joint boot missing or no longer prevents the ingress of dirt etc, 2% of tests (1.31x the national rate for this defect)
10. Windscreen washers not working or not providing sufficient fluid to clear the windscreen, 2% of tests (1.2x the national rate for this defect)

From 43,420 DVSA-tracked diesel Mercedes-Benz B-Class tests, 2024, split out from the Mercedes-Benz B-Class's other fuel types. DVSA testers marked 5.94% of these flagged defects as "dangerous", against 5.11% nationally. See which fuel type fails on the most dangerous defects nationally for how that compares across the whole fleet.

Most common MOT advisories on a diesel Mercedes-Benz B-Class

Flagged but doesn't fail the car, a different list from the failures above.

1. A flexible brake hose excessively damaged, deteriorated, chafed, twisted or stretched, 1.8% of tests (3.13x the national rate for this defect)
2. Brake pipe damaged or excessively corroded, 11.4% of tests (1.84x the national rate for this defect), also fails
3. A wheel badly distorted or wear between wheel and hub at spigot mounting, 2% of tests (1.83x the national rate for this defect)
4. Brake disc or drum significantly and obviously worn, 5.5% of tests (1.73x the national rate for this defect)
5. A tyre seriously damaged, 19.1% of tests (1.24x the national rate for this defect), also fails
6. Tyre tread depth not in accordance with the requirements, 25.7% of tests
7. Brake disc or drum excessively weakened, insecure or fractured, 12.9% of tests
8. a brake lining or pad worn below 1.5mm, 9.8% of tests
9. A suspension pin, bush or joint excessively worn, 5.3% of tests
10. A spring or spring component fractured or seriously weakened, 3.7% of tests, also fails

From 43,420 DVSA-tracked diesel Mercedes-Benz B-Class tests, 2024.

Other Mercedes-Benz B-Class fuel types

• Petrol Mercedes-Benz B-Class - 75.2%
• Electric Mercedes-Benz B-Class - 84.5%

All Mercedes-Benz B-Class MOT data · Every model