Porsche Cayenne S Diesel

It’s hard to ignore the Cayenne S Diesel’s blend of attributes. If you want a fast, upmarket and spacious SUV that handles well, the Porsche ticks all the boxes. Great refinement and a luxury interior add to its desirability, while the smart styling ensures it has plenty of kerb appeal. Options are costly and the BMW is cleaner, but there’s little else to fault.

Thanks to their menacing size, brash styling and thirst for fuel, performance SUVs aren’t universally loved. So for most owners it’s probably a good thing that the new Cayenne S Diesel doesn’t shout about its performance quite as much as more extrovert petrol models such as the Turbo and Turbo S.

The white paint, optional 21-inch wheels and black roof rails provide our test model with some menace, and the Cayenne’s once derided shape has evolved into a smart, well proportioned design that’s more modern than the dated X5.

Inside, you’ll find the same first-class driver-focused layout as in other Porsches. With controls that wrap around you, the new model almost has a sports car feel and the quality of materials and switchgear is superb, plus the traditional five-pod Porsche instrument panel adds to the character.

Plastics are smarter than in the BMW, while our car’s full leather interior and adaptive sports seats add to the cosy feel. There’s a huge range of adjustment and the supportive seats give an ideal driving position.

Yet despite the sports car ambience, the Cayenne’s size ensures you get a lofty view of the road and all-round visibility is excellent.

There’s lots of cabin stowage and the rear seats slide and fold 60:40. Legroom is a match for that of the X5, but while the outer seats are sculpted and comfortable, the middle one is narrow and flat, so the BMW’s single bench is better if you regularly carry three people.

Still, the Porsche has an extra 50 litres of luggage space, offering 670 litres with the rear seats in place. Obviously this is important, yet these SUVs trade as much on handling and performance as practicality.

The Cayenne doesn’t disappoint on that score, either. As soon as you turn the key, the V8 idles with a smooth, yet purposeful grumble, while the optional sports tailpipes produce a surprisingly petrol-like soundtrack.

The 4.2-litre V8 is borrowed from Audi, but Porsche has fitted unique internals to deliver 41bhp and 50Nm more than this engine offers in the Q7. Coupled with a sporty throttle response, the quick-revving 377bhp twin-turbo provides instant acceleration, while the mighty 850Nm of torque gives a seemingly never-ending wave of thrust.

At the test track, the Cayenne covered 0-60mph in just 5.3 seconds and was quicker to respond than the X5 in all but seventh gear. On the road it’s almost unnervingly fast for a vehicle of this size and weight, although it has the dynamic ability to cope with this.

Reactions are sharper than the BMW’s, and the steering is fast and precise with more natural weighting. Body movement is well controlled and, even though the X5 is only 30kg heavier, the Cayenne feels more agile.

There’s so much grip on offer that you’d do well to get close to the limit within the confines of the road, but at the test track you can feel the chassis hunkering down as the optional torque vectoring helps keep the Cayenne on its line.

The Porsche is also more relaxing – it follows cambers in the road less than the X5, and with the £2,379 air-suspension fitted, the ride is cushioned and comfortable. However, the weight and size of the optional 21-inch wheels mean the Cayenne crashes into potholes, taking the edge off the otherwise excellent refinement. If you want to avoid this trait, stick with the standard 18-inch alloys.

The eight-speed Tiptronic auto doesn’t have the razor-sharp shifts of Porsche’s dual-clutch PDK, but it’s smooth and, matched to stop-start and coasting functions, helps economy. The car returned 29.3mpg on test, although it emits more CO2 than the BMW, at 218g/km.

And while the Porsche is nearly £2,000 cheaper than the M50d, you have to be careful not to get carried away with the options list – our test car nudged past the £75,000 mark with extras fitted. Nevertheless, the new Cayenne S Diesel’s mix of performance, comfort and luxury is hard to ignore.