BMW Z4 running costs and mpg

• All-petrol line-up could be thirsty
• M40i the least frugal option
• Driven carefully you could get close to 40mpg

As a sporty roadster, the Z4’s running costs aren’t its main selling factor, but it could turn out to be more economical than you might think.

The best performer in the range is the entry-level sDrive20i, with 38.7-39.8mpg achievable according to BMW. Even the sDrive30i isn’t far behind despite its higher power output, claiming 37.7-38.7mpg.

Unsurprisingly it’s the M40i with the lowest claimed fuel economy figures, achieving up to 33.2mpg. If, however, you make the most of its 340hp engine then you’ll see less than 30mpg with ease.

Both the 20i and 30i emit 139g/km of CO2, while the M40i produces 168g/km, which isn’t too bad considering the power.

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Is it reliable?

• No recalls for the Z4 so far
• We’ve experienced some tech niggles
• Three-year warranty as standard

BMW has a good reputation for building solid and dependable cars, and there’s little reason to believe the Z4 will buck this trend. The engines are found in several other models and are proven to be trustworthy.

We’ve found a couple of issues with the firm’s latest infotainment system, though. In some time with the 3 Series and 8 Series, we experience it regularly disconnecting the Apple CarPlay connection, which can become tiresome. It could well just be a small issue that a software update would fix.

We’ve also found the wireless chargers in some cars can get very hot, but there’s no report on if this is normal or not.

For peace of mind, the Z4 comes with BMW’s three-year, unlimited-mileage warranty to keep you covered if things do go wrong.