2017 Mercedes-Benz B-Class — MOT failures & pass rate
Across 31,974 MOT tests, the 2017 Mercedes-Benz B-Class recorded an 88.7% pass rate. That is 2.3 percentage points better than MPVs of a similar age, which fail at 13.6%. Failures cluster in tyres, lighting & signalling and suspension.
What the MOT record shows
No single area dominates — tyres (5.7%) and lighting & signalling (3.6%) 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), headlamp aim and tread depth — registration plate lamp(s) alone was recorded 825 times.
A 150k+ example is materially riskier than a 0-30k one: 20.4% versus 7.0%.
Split by fuel, diesel examples fail 3.2pp more often than petrol ones (11.8% vs 8.6%) — worth weighing if you have a choice.
Advisories point at the next bill rather than this one: tyres was flagged on 24.3% of tests without failing them.
The trend is worsening — 7.8% of tests failed in 2021 against 14.4% in 2025, the usual pattern as a fleet ages.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Tyres | 5.7% | 1,830 |
| 2 | Lighting & signalling | 3.6% | 1,159 |
| 3 | Suspension | 1.9% | 602 |
| 4 | Visibility | 1.7% | 549 |
| 5 | Brakes | 1.6% | 503 |
| 6 | Emissions & environmental | 1.1% | 341 |
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) | 825 |
| 2 | Headlamp aim | 458 |
| 3 | Tread depth | 418 |
| 4 | Coil spring | 415 |
| 5 | Brake pads | 403 |
| 6 | Wipers | 326 |
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 | 24.3% | 7,764 |
| 2 | Brakes | 13.7% | 4,384 |
| 3 | Other defects | 6.4% | 2,053 |
| 4 | Visibility | 2.8% | 899 |
| 5 | Lighting & signalling | 2.2% | 707 |
| 6 | Suspension | 2.0% | 647 |
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 | 10,933 | 7.0% |
| 30-60k | 15,295 | 12.0% |
| 60-90k | 4,653 | 16.7% |
| 90-120k | 895 | 20.1% |
| 120-150k | 144 | 19.4% |
| 150k+ | 54 | 20.4% |
Failure rate by age
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Diesel | 26,386 | 11.8% |
| Petrol | 4,996 | 8.6% |
| Electric | 589 | 10.7% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 6,198 | 7.8% |
| 2022 | 6,283 | 9.3% |
| 2023 | 6,482 | 11.9% |
| 2024 | 6,446 | 12.8% |
| 2025 | 6,565 | 14.4% |
What to check before buying a 2017 B-Class
On a 2017 B-Class, tyres is what the MOT record says goes wrong most — it appeared in 5.7% of tests. Check these areas before you commit.
- Tyres (5.7% 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 (3.6% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Suspension (1.9% 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 2017 Mercedes-Benz B-Classs pass their MOT?
88.7% of the 31,974 2017 Mercedes-Benz B-Class MOT tests in this dataset passed — a 11.3% fail rate.
What is the most common MOT failure on a 2017 Mercedes-Benz B-Class?
Tyres, recorded in 5.7% of tests, followed by lighting & signalling (3.6%).
Does the 2017 B-Class get worse with mileage?
Its MOT fail rate rises from 7.0% in the 0-30k band to 20.4% in the 150k+ band.
Methodology & source. Based on 31,974 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.