BMW 4 Series vs Mercedes-Benz SLK
On MOT-testable defects the BMW 4 Series comes out ahead: 11.8% of its tests record a failure against 19.4% for the Mercedes-Benz SLK, a 7.7-point gap. The biggest single difference is suspension, where the SLK records failures noticeably more often.
11.8%
4 Series fail rate
19.4%
SLK fail rate
7.69pp
Difference
Side by side
| Metric | BMW 4 Series | Mercedes-Benz SLK |
|---|---|---|
| MOT tests analysed | 567,497 | 354,328 |
| Pass rate | 88.2% | 80.5% |
| Fail rate | 11.8% | 19.4% |
Where they differ
| Category | 4 Series | SLK |
|---|---|---|
| Suspension | 1.4% | 9.1% |
| Lighting & signalling | 2.4% | 7.0% |
| Brakes | 1.9% | 5.1% |
| Tyres | 7.3% | 5.1% |
| Visibility | 1.6% | 2.6% |
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.