Bmw Z4 vs Porsche Boxster
On MOT-testable defects, the Porsche Boxster (fail rate 13.8%) performed better than the Bmw Z4 (17.1%) across comparable years. The biggest divergence was emissions & environmental, where the Boxster recorded failures more often.
17.1%
Z4 fail rate
13.8%
Boxster fail rate
3.26pp
Difference
Side by side
| Metric | Bmw Z4 | Porsche Boxster |
|---|---|---|
| MOT tests analysed | 203,942 | 182,460 |
| Pass rate | 82.9% | 86.2% |
| Fail rate | 17.1% | 13.8% |
Where they differ
| Category | Z4 | Boxster |
|---|---|---|
| Emissions & environmental | 0.0% | 3.9% |
| Visibility | 3.3% | 0.0% |
| Tyres | 5.1% | 2.7% |
| Suspension | 5.7% | 3.8% |
| Brakes | 4.8% | 3.6% |
| Lighting & signalling | 5.4% | 6.1% |
Methodology & source. Dataset: DVSA MOT testing data (2021,2022,2023,2024,2025). Data last updated 2026-07-01. Figures reflect MOT-testable defects only — read the methodology for how these are calculated and what they don't measure.