2012 Mercedes-Benz B-Class — MOT failures & pass rate
Across 36,242 MOT tests, the 2012 Mercedes-Benz B-Class recorded an 80.5% pass rate. That is 3.2 percentage points better than MPVs of a similar age, which fail at 22.7%. Failures cluster in suspension, lighting & signalling and tyres.
What the MOT record shows
No single area dominates — suspension (8.2%) and lighting & signalling (7.6%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are linkage ball joint dust cover, coil spring and rigid brake pipes — linkage ball joint dust cover alone was recorded 1,324 times.
Condition tracks the odometer closely. Failures run at 8.8% in the 0-30k band and 25.0% in the 150k+ band, a 16.3-point spread — more than double.
The petrol cars hold up better: 16.7% fail against 20.6% for diesel, a 3.9-point gap across 36,242 tests.
Tyres is the most common advisory, noted on 25.2% of tests — work that passed today but is likely due soon.
The trend is worsening — 18.0% of tests failed in 2021 against 20.7% in 2025, the usual pattern as a fleet ages.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Suspension | 8.2% | 2,974 |
| 2 | Lighting & signalling | 7.6% | 2,742 |
| 3 | Tyres | 5.9% | 2,137 |
| 4 | Brakes | 4.5% | 1,616 |
| 5 | Emissions & environmental | 2.5% | 905 |
| 6 | Visibility | 2.4% | 858 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Linkage ball joint dust cover | 1,324 |
| 2 | Coil spring | 1,195 |
| 3 | Rigid brake pipes | 1,053 |
| 4 | Headlamp aim | 1,040 |
| 5 | Registration plate lamp(s) | 1,038 |
| 6 | Malfunction indicator lamp | 838 |
Top advisory categories
Advisories aren't failures, but they flag work likely needed soon — useful when budgeting.
| # | Category | % of tests with advisory | Tests |
|---|---|---|---|
| 1 | Tyres | 25.2% | 9,128 |
| 2 | Brakes | 24.7% | 8,963 |
| 3 | Suspension | 12.7% | 4,600 |
| 4 | Other defects | 8.3% | 3,003 |
| 5 | Visibility | 3.5% | 1,265 |
| 6 | Lighting & signalling | 2.6% | 940 |
Failure rate by mileage
Higher-mileage cars tend to fail more — often the most useful guide to real condition.
| Mileage band | Tests | Fail rate |
|---|---|---|
| 0-30k | 1,219 | 8.8% |
| 30-60k | 9,361 | 15.0% |
| 60-90k | 13,910 | 20.6% |
| 90-120k | 7,993 | 22.7% |
| 120-150k | 2,790 | 23.3% |
| 150k+ | 963 | 25.0% |
Failure rate by age
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Diesel | 26,153 | 20.6% |
| Petrol | 10,089 | 16.7% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 7,273 | 18.0% |
| 2022 | 7,222 | 18.4% |
| 2023 | 7,344 | 20.0% |
| 2024 | 7,274 | 20.6% |
| 2025 | 7,129 | 20.7% |
What to check before buying a 2012 B-Class
The failure pattern for this year is specific enough to inspect against: suspension accounted for 8.2% of tests. Start there.
- Suspension (8.2% of tests): Worn drop links, bushes, springs or shocks — listen for knocks over bumps and check for uneven tyre wear. Typical repair: £150–£450 per corner.
- Lighting & signalling (7.6% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Tyres (5.9% of tests): Usually a quick, known-cost fix, but check tread, age and uneven wear (which can hint at alignment or suspension issues). Typical repair: £50–£120 per tyre.
Repair costs are rough UK ballpark ranges to set expectations, not quotes — actual prices vary widely by car, parts and garage.
Frequently asked questions
How many 2012 Mercedes-Benz B-Classs pass their MOT?
80.5% of the 36,242 2012 Mercedes-Benz B-Class MOT tests in this dataset passed — a 19.5% fail rate.
What is the most common MOT failure on a 2012 Mercedes-Benz B-Class?
Suspension, recorded in 8.2% of tests, followed by lighting & signalling (7.6%).
Does the 2012 B-Class get worse with mileage?
Its MOT fail rate rises from 8.8% in the 0-30k band to 25.0% in the 150k+ band.
Methodology & source. Based on 36,242 MOT tests. Dataset: DVSA MOT testing data (2021,2022,2023,2024,2025). Data last updated 2026-07-27. Figures reflect MOT-testable defects only — read the methodology for how these are calculated and what they don't measure.