2015 Mercedes-Benz B-Class — MOT failures & pass rate
The 2015 Mercedes-Benz B-Class passed 86.2% of its 32,705 recorded MOT tests. That is 3.4 percentage points better than MPVs of a similar age, which fail at 17.2%. Failures cluster in tyres, lighting & signalling and suspension.
What the MOT record shows
No single area dominates — tyres (6.1%) and lighting & signalling (5.4%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are registration plate lamp(s), coil spring and headlamp aim — registration plate lamp(s) alone was recorded 1,193 times.
A 150k+ example is materially riskier than a 0-30k one: 19.8% versus 7.9%.
Split by fuel, diesel examples fail 3.7pp more often than petrol ones (14.3% vs 10.7%) — worth weighing if you have a choice.
Advisories point at the next bill rather than this one: tyres was flagged on 25.8% of tests without failing them.
The trend is worsening — 10.8% of tests failed in 2021 against 16.3% in 2025, the usual pattern as a fleet ages.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Tyres | 6.1% | 1,994 |
| 2 | Lighting & signalling | 5.4% | 1,780 |
| 3 | Suspension | 3.9% | 1,258 |
| 4 | Brakes | 2.1% | 700 |
| 5 | Visibility | 1.9% | 626 |
| 6 | Emissions & environmental | 1.5% | 476 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Registration plate lamp(s) | 1,193 |
| 2 | Coil spring | 775 |
| 3 | Headlamp aim | 648 |
| 4 | Brake pads | 569 |
| 5 | Tread depth | 556 |
| 6 | Linkage ball joint dust cover | 488 |
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 | 25.8% | 8,442 |
| 2 | Brakes | 16.7% | 5,445 |
| 3 | Other defects | 6.7% | 2,183 |
| 4 | Suspension | 4.8% | 1,553 |
| 5 | Visibility | 3.0% | 984 |
| 6 | Lighting & signalling | 2.1% | 703 |
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 | 4,385 | 7.9% |
| 30-60k | 15,173 | 12.3% |
| 60-90k | 9,416 | 16.5% |
| 90-120k | 2,800 | 20.0% |
| 120-150k | 636 | 19.8% |
| 150k+ | 288 | 19.8% |
Failure rate by age
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Diesel | 27,863 | 14.3% |
| Petrol | 4,354 | 10.7% |
| Electric | 488 | 12.1% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 6,346 | 10.8% |
| 2022 | 6,462 | 12.4% |
| 2023 | 6,583 | 14.0% |
| 2024 | 6,623 | 15.3% |
| 2025 | 6,691 | 16.3% |
What to check before buying a 2015 B-Class
On a 2015 B-Class, tyres is what the MOT record says goes wrong most — it appeared in 6.1% of tests. Check these areas before you commit.
- Tyres (6.1% 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.
- Lighting & signalling (5.4% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Suspension (3.9% 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.
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 2015 Mercedes-Benz B-Classs pass their MOT?
86.2% of the 32,705 2015 Mercedes-Benz B-Class MOT tests in this dataset passed — a 13.8% fail rate.
What is the most common MOT failure on a 2015 Mercedes-Benz B-Class?
Tyres, recorded in 6.1% of tests, followed by lighting & signalling (5.4%).
Does the 2015 B-Class get worse with mileage?
Its MOT fail rate rises from 7.9% in the 0-30k band to 19.8% in the 150k+ band.
Methodology & source. Based on 32,705 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.