Mercedes-Benz SLK vs Porsche 911
The Porsche 911 has the better MOT record of the two — 9.7% fail rate versus 19.4% for the Mercedes-Benz SLK across comparable years. The biggest single difference is suspension, where the SLK records failures noticeably more often.
19.4%
SLK fail rate
9.7%
911 fail rate
9.8pp
Difference
Side by side
| Metric | Mercedes-Benz SLK | Porsche 911 |
|---|---|---|
| MOT tests analysed | 354,328 | 252,686 |
| Pass rate | 80.5% | 90.3% |
| Fail rate | 19.4% | 9.7% |
Where they differ
| Category | SLK | 911 |
|---|---|---|
| Suspension | 9.1% | 1.6% |
| Brakes | 5.1% | 2.0% |
| Tyres | 5.1% | 2.3% |
| Visibility | 2.6% | 0.0% |
| Lighting & signalling | 7.0% | 4.8% |
| Emissions & environmental | 0.0% | 1.9% |
Methodology & source. 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.