Sporting BMWs may have been inseparably associated with six cylinder engines down the years but the key powerplants on offer in this 'G29'-series Z4 line-up squirt fuel into the quartet of cylinders boasted by a TwinPower Turbo 2.0-litre unit that's offered in two states of tune. The 197hp sDrive 20i and 258bhp sDrive 30i variants are more powerful than the models they most directly replace; even the sDrive 20i can make 62mph from rest in just 6.6s on the way to 149mph. At the top of the range, you can have a traditional BMW straight-six unit, courtesy of the 340hp unit fitted to the flagship M40i derivative, which sprints to 62mph in 4.6s and has to be artificially restrained at 155mph.
You can talk to your dealer about a manual version of the base sDrive 20i, but otherwise, all variants come fitted with an 8-speed Steptronic Sport auto gearbox with gearshift paddles. You're probably going to want to pay extra for adaptive damping - only the M40i gets it as standard, along with uprated brakes and an electronically controlled differential lock. The way the suspension interacts with the steering, the throttle and the differential is key to the way this car responds dynamically, so proactive use of the provided drive modes is crucial if you're pressing on.
Perhaps the biggest news from a design point of view is the decision to replace the previous model's metal folding roof with a fabric top. The change really was a no-brainer. The new soft roof operates in around ten seconds, about twice as quick as the previous tin top. Plus it lets in less noise on the move and slightly lowers the centre of gravity. More practically, it allows for the same amount of luggage space whether the roof is up or down (265-litres) instead of the previous car's 310-litre roof-up / 180-litre roof-down unhappy compromise. In proper roadster style, there are no rear seats.
At the wheel, it's nicer than a 718 Boxster, which is presumably what BMW was aiming at. The level of fit and finish are almost faultless and there's a lot more interior space and storage than you'd expect to find in a roadster. There's also plenty of evidence that the Z4 has entered the digital age. You get the same fully digital instrument cluster that's found on the brand's latest 3 Series and 8 Series models. And a huge 10.25-inch centre-dash iDrive infotainment screen. This features an adaptive navigation system, a hard-drive-based multimedia system, two USB ports, plus Bluetooth and Wi-Fi interfaces.
List prices suggest that, allowing for a few well-chosen extras, you'll probably be paying somewhere in the £37,000 to £50,000 bracket for your Z4. Almost all BMW's business here is done with the four cylinder 2.0-litre petrol engine that powers the sDrive20i and 30i variants, leading to an average Z4 purchase price in the £40,000 to £45,000 bracket. There's an £8,500 step up from the sDrive 30i to the M40i, so you've really got to want that flagship model's six cylinder engine.
The list of options includes Active Cruise Control with Stop & Go function, plus there are various Driving Assistant systems, as well as a BMW's 'Parking Assistant' package, including a 'Reversing Assistant' feature that can reverse the car back automatically along the path just taken. This Z4 is also the first roadster to be made available (as an option) with a Head-Up Display. Safety can be given a further boost by opting for the Adaptive LED headlights. And with the optional Comfort or Comfort Plus packages fitted, the soft-top can be operated using the car key. The ambient lighting, fitted as standard, brings a particularly atmospheric mood to the cabin. LED fibre-optic guides light up the instrument panel's accent strips on either side of the steering wheel and provide indirect illumination of the centre console's edging, accentuating the areas of the cockpit of most importance for focused driving.
These days, even barnstorming sports cars need to keep running costs in check while treating the environment with kid gloves. The Z4 does a better job of this than you'd credit for a car in such a lofty performance bracket, mainly thanks the BMW's EfficientDynamics programme. Thanks to this, assuming you keep an eye on the optimal gearshift indicator, you should be able to get somewhere close to a combined cycle fuel figure which for the four cylinder engine is quoted at around 49mpg on the combined cycle, whichever state of tune you order it in - sDrive20i or 30i. And 138g/km of CO2. As for the six cylinder M40i model, well you're looking at 33.2mpg and 165g/km.
Routine maintenance is dictated by 'Condition Based Servicing' that monitors oil level and engine wear, taking into account how long it's been and how far the car has travelled since its previous garage visit. To help plan ahead for the cost of regular work, at point of purchase you'll be offered a 'BMW Service Inclusive' package that lasts for three years and 36,000 miles. BMW offers a warranty that lasts for three years, no matter how many miles you complete.
For the magazines, the definition of success for this MK3 model Z4 will lie in whether it handles just like the equivalent Porsche Boxster. But for most potential owners, that won't be the over-riding priority. BMW has been building roadsters for over 80 years - and it shows with this third generation design, a model that's matured extremely well, slowly and methodically developing into an all-rounder that's tough to beat.
In fact, I can't help feeling that this is probably the ideal car of its kind for most potential buyers. True, it isn't the driver's machine that its Porsche rival can be but it gets close enough for many likely customers to start prioritising the lower pricing and nicer cabin that you get with this Munich model. What it all means is that though the Z4 might not be the first car you look at when choosing a sports roadster, look at it you must. It's now just too good not to.