Mercedes-Benz B-Class: MOT pass rate and reliability data

The Mercedes-Benz B-Class fails its first MOT more often than the average UK car, by 2 percentage points. These figures come from the DVSA's full year of anonymised MOT results, covering 63,986 individual Mercedes-Benz B-Class tests. Nothing here is an estimate or a survey.

The numbers

First-time pass rate74.7%
UK national average76.7%
Difference-2 points
Tests analysed63,986
Average mileage at test73,962 miles
Average year of manufacture2013
Reliability rank1,630 of 2,005 models

What this means if you are buying one

A 74.7% first-time pass rate means roughly 25 in every 100 Mercedes-Benz B-Class presented for MOT fail on the first attempt. That is worse than average, so budget for remedial work and treat a fresh 12-month MOT as a genuine selling point rather than a given. The average Mercedes-Benz B-Class tested had covered 73,962 miles and was built around 2013.

What this means at salvage auction

Pass rate is a proxy for what a car costs to keep on the road. The Mercedes-Benz B-Class sits 2 points below the national average, ranked 1,630 of 2,005 models. On one bought as repairable salvage, assume the mechanical side needs more than the visible accident damage, and pad your repair estimate accordingly.

Before you bid: run the lot through the analyzer, check the car's own record, check the mileage, decode the VIN, and if it carries a marker use the write-off value calculator. Or compare it against another model.

Looking at a specific Mercedes-Benz B-Class rather than the model in general? The free check covers its MOT and mileage history, and the full HPI report confirms the insurance write-off category, outstanding finance and whether it is recorded stolen, from licensed data for 5 credits. Already own one that has been damaged? Work out whether fixing it beats selling it with the repair or scrap calculator, and see the median recorded closing bid for a damaged Mercedes-Benz B-Class: £925 at UK salvage auction, from 18 ended listings, not independently confirmed sales.

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

  1. A direction indicator lamp missing, inoperative or in the case of a multiple light source more than 1/2 not functioning, 1.8% of tests (2.75x the national rate for this defect)
  2. A suspension joint dust cover missing or no longer prevents the ingress of dirt etc, 4.9% of tests (2.66x the national rate for this defect)
  3. A rear registration plate lamp or light source missing or inoperative in the case of a single lamp or all lamps, 2.2% of tests (2.46x the national rate for this defect)
  4. Brake pipe damaged or excessively corroded, 2.3% of tests (2.12x the national rate for this defect)
  5. Lamp emitted colour, position or intensity not in accordance with the requirements, 1.3% of tests (2.1x the national rate for this defect)
  6. A transmission shaft constant velocity joint boot missing or no longer prevents the ingress of dirt etc, 2.9% of tests (1.88x the national rate for this defect)
  7. A spring or spring component fractured or seriously weakened, 4.1% of tests (1.79x the national rate for this defect)
  8. Engine MIL illuminated indicating a malfunction, 2.1% of tests (1.65x the national rate for this defect)
  9. A tyre seriously damaged, 4.2% of tests (1.51x the national rate for this defect)
  10. Windscreen washers not working or not providing sufficient fluid to clear the windscreen, 2.3% of tests (1.37x the national rate for this defect)

From 63,931 DVSA-tracked Mercedes-Benz B-Class tests, 2024. DVSA testers marked 5.49% of these flagged Mercedes-Benz B-Class defects as "dangerous", meaning the tester judged the car unsafe to drive away, against 5.11% nationally.

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

An advisory doesn't fail the car - the tester flags it as worth watching, but it still passes. A different list from the failures above: what testers are noting on a Mercedes-Benz B-Class before it actually fails on it.

  1. A flexible brake hose excessively damaged, deteriorated, chafed, twisted or stretched, 2.2% of tests (3.86x the national rate for this advisory)
  2. Brake pipe damaged or excessively corroded, 12.9% of tests (2.09x the national rate for this advisory), also fails
  3. Brake disc or drum significantly and obviously worn, 5.2% of tests (1.63x the national rate for this advisory)
  4. A wheel badly distorted or wear between wheel and hub at spigot mounting, 1.6% of tests (1.5x the national rate for this advisory)
  5. Lamp emitted colour, position or intensity not in accordance with the requirements, 1.8% of tests (1.32x the national rate for this advisory), also fails
  6. A tyre seriously damaged, 19.4% of tests (1.26x the national rate for this advisory), also fails
  7. Tyre tread depth not in accordance with the requirements, 23.9% of tests
  8. Brake disc or drum excessively weakened, insecure or fractured, 12.5% of tests
  9. a brake lining or pad worn below 1.5mm, 9.6% of tests
  10. A suspension pin, bush or joint excessively worn, 5.3% of tests

From 63,931 DVSA-tracked Mercedes-Benz B-Class tests, 2024.

Mercedes-Benz B-Class pass rate by model year

From its 2005 to its 2019 model year, the Mercedes-Benz B-Class's first-time pass rate has risen 25.9 points, from 65.6% to 91.5%, the usual pattern: a newer model year is a younger car today, so it fails less. First-time pass rate for each Mercedes-Benz B-Class year:

Mercedes-Benz B-Class by fuel type

The Mercedes-Benz B-Class's two most-tested fuel types split by 0.1 points: diesel passes first time 75.1% of the time (43,228 tests) against 75.2% for petrol (19,996 tests).

Other Mercedes-Benz models

Models with a similar pass rate

If this car is a salvage or write-off

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Mercedes-Benz B-Class MOT pass rate badge: 74.7%

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Mercedes-Benz B-Class most common MOT failure: A direction indicator lamp missing, inoperative or in the case of a multiple light source more than 1/2 not functioning (1.8% of tests)

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All 2,005 models ranked by MOT pass rate