What’s new: This is the entry 2.5-litre 23i version of BMW‘s new Z4, the first production car from the company that features a retractable hard-top roof, folding in 20 seconds.

Excellent: The cost per mile of 59.9p is 4.6p better than the 3.0-litre version, helped by a mighty 51.5% predicted residual value. It also has a P11D that’s £4000 cheaper than the next model up.

Good: The average fuel economy figure of 33.2mpg isn’t bad for a 207PS roadster, and we averaged more than 30mpg despite some spirited driving. There are also a good spread of cabin storage cubbyholes and bins.

Average: A CO2 figure of 199g/km isn’t bad for a sports car, which puts the BMW in the 27%?benefit-in-kind tax band.

Poor: The folding hard-top is great for refinement and security but it eats boot space. The Z4 has 60 litres in hand over the Audi TT Roadster with the roof up, but drops 70 behind when its folded.

Verdict: The cheapest Z4 is possibly the one to have – it offers enough performance for a decent P11D.

BMW Z4 sDrive 23i
P11D price £28,380
Model price range £28,380-£37,065
Fuel consumption 33.2mpg
CO2 (tax) 199g/km (27%)
BIK 20/40% per month £128/£255
Service interval variable mls
Insurance group 17
Warranty 3yrs/unltd mls
Boot space (min/max) 180/310 litres
Engine size/power 2479cc/207PS
Top speed/0-62mph 149mph/6.6secs
On sale May 2009
Score 8/10
Verdict Cheapest version of the new
roadster could be the best bet,
though a little more power
wouldn’t have been a bad thing.