Sector: Sports car Price: £44,760 Fuel: 31.4mpg CO2: 210g/km

The Z4 nameplate has been with us for ten years now, and even this second generation version has just come around to its first refresh. It’s had a lifespan marked by turbulence in the motor industry, and while the distinctive silhouette with its mile-long bonnet, set-back cabin and squared-off rear wings hasn’t changed much, the technology underneath is very different.

So the sDrive35i a bit of a rarity. Alongside its more focused sDrive35iS sibling, this is now the only two-seat BMW with the carmaker’s trademark straight-six petrol engine. In this case, it’s a slightly less powerful version of the 3.0-litre twin turbocharged unit found in the M135i. It makes the Z4 a bit of a muscle car, packing 306bhp and the ability to reach 62mph in 5.1 seconds.

But that’s only half the story. Z4s of old came alive at the top of the rev range, but the 35i is an entirely different engine. Its twin-turbochargers give the sort of responsiveness usually only found in cars with over 400bhp, an electrifying surge of power at almost any point in the rev range, and with the dual-clutch gearbox in Sport it’ll keep pulling for as long as you keep your toes down.

Why is this so important? Well, these days a lot of performance cars are so well engineered that figures which would’ve been enough for supercar owners to brag about not so long ago now feel a little effortless. The Z4 still feels as engaging as the sports cars of old – it’s a fast car, and it feels it.

Even down to the noise it makes. A purposeful growl at the bottom of the rev range, rising to a shrill supercar-like howl above 5,000rpm to give away just how well endowed it is. Somewhere there’s an engineer who’ll have spent a lot of time making this sound the way it does – he or she deserves a pay rise.

Everything else delights, too. The brakes are positive without being grabby, the gearbox is quick to put you in the right gear and doesn’t hesitate off the mark and although the engine adds a weight to the front end it’s only noticeable on the sharpest of corners. There’s still a slight numbness to the steering, but for an electronic system it feels mechanical enough to suit a sports car like this.

While this is very much a car built to take challenging roads in its stride, it’s in no way challenging to live with. The cabin is, unsurprisingly, small but the seats are comfortable and high speed refinement is impressive with the roof up. There’s even a ski hatch between the seats, if you’re prepared to travel long distances with a bag between you and your passenger.

But customers are voting with their feet. The biggest selling Z4 is the sDrive20i, with a four-cylinder petrol engine, and while it sounds like BMW is abandoning its iconic straight-sixes you can understand why buyers aren’t missing them much. All four-cylinder Z4s emit less than 160g/km of CO2, and even the new 156bhp sDrive18i doesn’t feel like half the car, despite having half the power.

Ultimately, though, a car like this is never going to make sense purely on a rational basis. The sDrive35i does everything a BMW sports car should do well, but it’s an aspirational halo model descended from a long line of straight-six roadsters and long may it remain.

Verdict:

Rear seats aside, the Z4 is a very complete car – it’s quiet and comfortable when it needs to be, but with the muscle to become a near supercar-chasing two-seater when the mood takes you. But with the tide turning against speeding drivers and fuel costs continuing to spiral, its four-cylinder siblings offer almost all of the entertainment for considerably less cost.