Sector: Compact Executive Price (June 2013): £28,830–£40,995 Fuel: 34.9–62.8mpg CO2: 119–189g/km

Buying a 3 Series used to be simple: a choice of saloon or Touring, coupe or convertible, all desirable new and used, sharing the same high dynamic abilities and powerful, efficient engines.

But the latest F30-generation 3 Series is part of a much larger family. The standard saloon and Touring are still in place, the coupe, convertible and a rumoured rival to the Audi A5 Sportback will be sold as the 4 Series, the X3 SUV is about to gain a sportier X4 sibling, and buyers looking for a bit of extra luxury will be shoehorned into the 3 Series Gran Turismo.

Given that the 5 Series GT hasn’t won over legions of  BMW buyers in the UK, you may be wondering where this new car is going. The 3 GT isn’t a direct A5 rival, and unlike the 5 GT it’s not based on a larger platform. Instead, the 3 Series GT is based on the long wheelbase F30 saloon sold in China, but with frameless windows and a higher, raked roofline.

A niche too far? Perhaps, but it does have its uses. Back-seat passengers are given 5 Series amounts of legroom with noticeably broader shoulder space and individually reclining backrests, and BMW was keen to point out the extra load length and shoulder room on offer. Ultimately there’s more space for bulky objects in a 3 Series Touring, but the ability to fit longer loads in the GT means it’s potentially more useful in real-world situations.

The big difference, though, is the way loads fit in. That long boot hatch means it’s even easier to get boxes into this than it is into a Touring, with which this shares a simple folding mechanism for its three-piece rear bench. There’s even a sculpted compartment under the boot floor, shaped to hold the dismantled pieces of parcel shelf in place.

UK sales are expected to peak at 4,000 units per year, of a total 37,000 3 Series models. The expected 60% fleet / 40% retail mix is on par with the saloon, and prices are between £1,300 and £1,600 higher than the equivalent Touring. Because all GT trim levels are fitted with 18-inch alloy wheels, there’s a £500 smaller price gain between trim levels – these comprise the familiar SE, Luxury, Sport and Modern line from the rest of the 3 Series family, completed by the M Sport this summer.

Almost all of the engines are also familiar, with 20i, 28i and 35i petrols and 18d and 20d diesels available from launch, and a four-wheel drive 20i xDrive and the 35d diesel to follow. Predictably, BMW expects the 320d GT to be the big seller, but there’s no EfficientDynamics version as in the saloon. As a result, the 318d GT is the most efficient of the range, with CO2 emissions of 119g/km and combined fuel consumption of 62.8mpg.

Although it lacks the punch of the fleet-favourite 20d engine, extra economy doesn’t completely blunt the 318d GT. There’s enough power available to make this a relaxed motorway car, only really let down by a lot of grumble at low speeds, and its 143bhp output is delivered progressively through the rev range. Despite a 140kg weight gain and the longer wheelbase, the GT feels almost as agile and fun to drive as the saloon.

As good as it is, though, it’s understandably a niche model. The 3 Series Touring is a known quantity on the used market, there’s only £920 between a 320d SE GT and a 520d saloon, and the larger car is more fuel efficient. It makes this a good car, but a model with limited appeal against the already strong 3 Series range.

Verdict:

Spacious, flexible and as good to drive as the rest of the 3 Series family, the Gran Turismo is a better fit for UK tastes than its 5 Series equivalent. But the higher pricing and slightly clumsier styling compared to the saloon or Touring could limit its appeal.

Watch the latest BMW 3 Series Gran Turismo video here.