2017 Mercedes-Benz Sl — MOT failures & pass rate
The 2017 Mercedes-Benz Sl passed 92.7% of its 3,458 recorded MOT tests. That is 2.5 percentage points better than coupes & convertibles of a similar age, which fail at 9.8%. Failures cluster in tyres, lighting & signalling and suspension.
What the MOT record shows
No single area dominates — tyres (4.5%) and lighting & signalling (1.6%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are headlamp aim, ball joint and tread depth — headlamp aim alone was recorded 52 times.
Condition tracks the odometer closely. Failures run at 6.2% in the 0-30k band and 14.6% in the 60-90k band, a 8.5-point spread — more than double.
Advisories point at the next bill rather than this one: tyres was flagged on 18.7% of tests without failing them.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Tyres | 4.5% | 155 |
| 2 | Lighting & signalling | 1.6% | 55 |
| 3 | Suspension | 1.2% | 40 |
| 4 | Visibility | 0.5% | 17 |
| 5 | Emissions & environmental | 0.5% | 17 |
| 6 | Brakes | 0.4% | 12 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Headlamp aim | 52 |
| 2 | Ball joint | 31 |
| 3 | Tread depth | 22 |
| 4 | Registration plates | 15 |
| 5 | Headlamp | 15 |
| 6 | Catalyst emissions | 13 |
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 | 18.7% | 647 |
| 2 | Brakes | 2.9% | 102 |
| 3 | Suspension | 2.9% | 101 |
| 4 | Other defects | 2.6% | 90 |
| 5 | Visibility | 2.5% | 86 |
| 6 | Road wheels | 1.0% | 36 |
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 | 2,332 | 6.2% |
| 30-60k | 972 | 8.6% |
| 60-90k | 123 | 14.6% |
Failure rate by age
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 703 | 6.0% |
| 2022 | 700 | 6.9% |
| 2023 | 711 | 8.0% |
| 2024 | 676 | 8.6% |
| 2025 | 668 | 6.9% |
What to check before buying a 2017 Sl
On a 2017 Sl, tyres is what the MOT record says goes wrong most — it appeared in 4.5% of tests. Check these areas before you commit.
- Tyres (4.5% 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 (1.6% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Suspension (1.2% 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.
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 Sls pass their MOT?
92.7% of the 3,458 2017 Mercedes-Benz Sl MOT tests in this dataset passed — a 7.3% fail rate.
What is the most common MOT failure on a 2017 Mercedes-Benz Sl?
Tyres, recorded in 4.5% of tests, followed by lighting & signalling (1.6%).
Does the 2017 Sl get worse with mileage?
Its MOT fail rate rises from 6.2% in the 0-30k band to 14.6% in the 60-90k band.
Methodology & source. Based on 3,458 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.