2015 Mercedes-Benz SLK — MOT failures & pass rate
The 2015 Mercedes-Benz SLK passed 87.1% of its 27,715 recorded MOT tests. That is effectively the same as coupes & convertibles of a similar age (11.9% fail rate), so the MOT record here is unremarkable in either direction. Failures cluster in tyres, suspension and lighting & signalling.
What the MOT record shows
No single area dominates — tyres (6.8%) and suspension (4.6%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are coil spring, tread depth and headlamp aim — coil spring alone was recorded 831 times.
A 120-150k example is materially riskier than a 0-30k one: 28.2% versus 7.0%.
The petrol cars hold up better: 9.4% fail against 14.3% for diesel, a 4.9-point gap across 27,715 tests.
Tyres is the most common advisory, noted on 24.4% of tests — work that passed today but is likely due soon.
The trend is worsening — 9.7% of tests failed in 2021 against 15.1% in 2025, the usual pattern as a fleet ages.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Tyres | 6.8% | 1,880 |
| 2 | Suspension | 4.6% | 1,267 |
| 3 | Lighting & signalling | 2.1% | 574 |
| 4 | Brakes | 1.8% | 486 |
| 5 | Visibility | 0.9% | 264 |
| 6 | Emissions & environmental | 0.9% | 244 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Coil spring | 831 |
| 2 | Tread depth | 779 |
| 3 | Headlamp aim | 482 |
| 4 | Ball joint | 231 |
| 5 | Anti-lock braking system | 214 |
| 6 | Ball joint dust cover | 213 |
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 | 24.4% | 6,758 |
| 2 | Brakes | 11.5% | 3,172 |
| 3 | Suspension | 7.7% | 2,132 |
| 4 | Other defects | 3.0% | 842 |
| 5 | Visibility | 2.5% | 691 |
| 6 | Road wheels | 1.6% | 452 |
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 | 7,434 | 7.0% |
| 30-60k | 14,805 | 13.5% |
| 60-90k | 4,583 | 18.5% |
| 90-120k | 742 | 22.5% |
| 120-150k | 117 | 28.2% |
Failure rate by age
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Diesel | 19,829 | 14.3% |
| Petrol | 7,886 | 9.4% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 5,469 | 9.7% |
| 2022 | 5,462 | 11.0% |
| 2023 | 5,567 | 13.4% |
| 2024 | 5,602 | 15.2% |
| 2025 | 5,615 | 15.1% |
What to check before buying a 2015 SLK
The failure pattern for this year is specific enough to inspect against: tyres accounted for 6.8% of tests. Start there.
- Tyres (6.8% 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.
- Suspension (4.6% 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 (2.1% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
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 SLKs pass their MOT?
87.1% of the 27,715 2015 Mercedes-Benz SLK MOT tests in this dataset passed — a 12.9% fail rate.
What is the most common MOT failure on a 2015 Mercedes-Benz SLK?
Tyres, recorded in 6.8% of tests, followed by suspension (4.6%).
Does the 2015 SLK get worse with mileage?
Its MOT fail rate rises from 7.0% in the 0-30k band to 28.2% in the 120-150k band.
Methodology & source. Based on 27,715 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.