Where each one leads
BMW Z4
- Against cars of the same age, the BMW Z4 comes out better at its first MOT test (passes 20% more often than average) than the Mercedes-Benz SLK (passes 16% more often than average).
- Fewer BMW Z4 cars in the Netherlands carry an illogical odometer record (4.2% against 9.5%).
Mercedes-Benz SLK
- New Mercedes-Benz SLK cars registered in Europe in 2020 average 153 g/km of CO₂ on the WLTP test, against 170 for the BMW Z4 in 2022.
Too close to call: official combined fuel use, Canada (l/100 km).
Only measures that do not depend on how many cars were sold: pass and failure rates against cars of the same age, ratings, fuel use and CO₂. How we compare
At a glance
| BMW Z4 | Mercedes-Benz SLK | |
|---|---|---|
| Model years in the US safety record | 2002–2025 | 1998–2012 |
| New cars registered in Europe | 60,724 (2010–2022) | 75,551 (2010–2020) |
| Licensed in the United Kingdom | 32,458 | 47,128 |
| On the road in the Netherlands | 5,299 | 9,739 |
| In traffic in Finland | 773 | 2,181 |
EEA new-car registrations (CC BY 4.0) · DVLA licensed vehicles (OGL v3.0) · RDW (CC0) · Traficom (CC BY 4.0) · generations: Wikidata (CC0).
Reliability and problems
| BMW Z4 | Mercedes-Benz SLK | |
|---|---|---|
| UK MOT first-time pass rate | 77% | 73% |
| … against cars of the same age | +20% | +16% |
| New York safety inspections failed | 1.0% | — |
| … against cars of the same year | −51% | — |
| Illogical odometer records (NL) | 4.2% | 9.5% |
| US owner complaints | 1,282 | 74 |
| Most complaints about | Steering | Visibility |
| Model year with most complaints | 2003 (414) | 2002 (25) |
| US recall campaigns | 28 | 3 |
| Manufacturer service bulletins | 1,817 | 79 |
| NHTSA defect investigations | 9 | 9 |
Complaint, recall and bulletin counts grow with the number of cars sold and are not adjusted for it. UK MOT: DVSA anonymised MOT results (OGL v3.0); New York: DMV inspections; complaints, recalls, bulletins and investigations: NHTSA (public domain); odometer: RDW (CC0).
Fuel, emissions and price
| BMW Z4 | Mercedes-Benz SLK | |
|---|---|---|
| Official combined fuel use, Canada | 8.4 l/100 km (2026) | 8.5 l/100 km (2016) |
| Real-world use in Europe, petrol | 8.9 l/100 km | — |
| Official CO₂ of new cars in Europe | 170 g/km | 153 g/km |
| Average power of new cars in Europe | 193 kW (259 hp) | 120 kW (161 hp) |
| Average mass in running order | 1,554 kg | 1,578 kg |
| Dutch list price when new (median) | €70,203 | €61,479 |
| Average odometer in Finland | 136,000 km | 175,000 km |
Canada: NRCan Fuel Consumption Ratings, most frugal version of the latest year (OGL Canada). Europe: EEA monitoring of new-car CO₂ and on-board fuel meters (OBFCM), CC BY 4.0. Price: RDW catalogue price (CC0). Finland: Traficom (CC BY 4.0).