BMW
Z4
Mercedes-Benz
SL
BMW Z4 vs Mercedes-Benz SL: 2025 Comparison
The short answer
Based on available data, the Mercedes-Benz SL comes out ahead of the BMW Z4 on fuel economy and power. Check the specs table and owner sentiment below for the full comparison before deciding between the two. Both are covered by real owner reports on CarWizz.
Specs side by side
What owners say
Z4
Overall
Sentiment is highly dependent on the specific generation and powertrain. For the current generation (G29), the Z4 M40i variant receives extremely positive feedback from owners, described as "insanely good," "stupid fast," "incredible power," "balanced," and "the best car I've ever owned." It is praised for its fun factor, driving dynamics, and value proposition, particularly when equipped with a manual transmission. The base 30i variant is considered competent but less memorable, with some reviewers labeling it "forgettable." The previous E89 generation (2009-2016) is viewed more as a comfortable grand tourer or "Palm Beach cruiser," with criticism for feeling heavy and sluggish.
Best version to buy
For the current generation (G29), the Z4 M40i is overwhelmingly recommended as the definitive version. Owners emphasize that the high-output B58 engine transforms the experience, making it "exceptional" and a "real weapon," whereas the lower-powered 30i variant does not leave the same impression.
Known issues
- ⚠**E85/E86 & E89 Generations:** Cooling system failures (water pumps, expansion tanks): common point of failure. Frequency: recurrent. Oil leaks (valve cover gaskets, oil filter housing): common with age. Frequency: recurrent.
- ⚠**G29 Generation:** Factory brake fluid inadequacy: noted as unsuitable for the car's performance level. Frequency: isolated. "Ass-backward" tachometer design: criticized layout. Frequency: isolated.
SL
Overall
Sentiment varies dramatically by generation and is heavily influenced by ownership expectations. The R129 generation (1990-2001) is universally praised in community feedback as a timeless, well-engineered, and durable classic, representing a peak in Mercedes-Benz build quality and engineering. The R230 generation (2002-2011) receives a mixed to negative assessment; while acknowledged as a wonderful driving car with excellent brake feel and comfort, it is described as a potential "albatross" due to a very high frequency of complex, expensive failures related to its hydraulic, pneumatic, and electronic systems.
Best version to buy
Insufficient owner data available for a single "best version" consensus across all trims and generations. For the R129, the V8-powered models (500SL/SL500) are mentioned as the most successful and sensible.
Known issues
- ⚠**R230 Generation (Very Frequent Themes):** * Trunk water leaks: Leads to multiple electrical failures. Frequency: very frequent.
- ⚠**R232 Generation (Recurrent Themes):** * Harsh ride quality: Described as rougher than any SL in history except for extreme AMG Black Series models. Frequency: recurrent.
- ⚠**General SL Issues:** * High maintenance costs: Routine and repair costs are extremely high, with reports of single service visits costing $4,000-$6,000. Frequency: very frequent.
The verdict
The Mercedes-Benz SL is the better choice for most buyers.
It has better fuel economy on its best-equipped version than the BMW Z4, based on the data above. If power matters more to you than running costs, the BMW Z4 is worth a closer look instead.
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Frequently asked questions
Which is more reliable, the BMW Z4 or the Mercedes-Benz SL?
Owner reports show similar reliability sentiment for the BMW Z4 and the Mercedes-Benz SL. Check the known issues listed above for specific differences between the two.
Which is better for families, the BMW Z4 or the Mercedes-Benz SL?
The Mercedes-Benz SL seats more passengers than the BMW Z4 on its catalogued best-equipped version. Body type also differs: the BMW Z4 is classed as a Roadster, the Mercedes-Benz SL as a Roadster.
Which has better fuel economy, the BMW Z4 or the Mercedes-Benz SL?
The Mercedes-Benz SL is more fuel-efficient on paper: 7.7 L/100km combined versus 9.4 L/100km for the BMW Z4, based on the best-equipped catalogued version of each.
Which is cheaper to maintain, the BMW Z4 or the Mercedes-Benz SL?
Exact maintenance costs aren't in our data, but owner reports mention cost-related concerns more often for the Mercedes-Benz SL than the BMW Z4. See the known issues comparison above.