BMW offers a very big range of diesel and petrol engines for the X5. And in May 2016 it added a plug-in hybrid drivetrain with the xDrive 40e (it teams a petrol engine with an electric motor whose battery can be charged from household power outlets).
Of the diesel and petrol cars, the least costly X5 – the sDrive 25d – uses least fuel, its 2.0-litre, four-cylinder turbo-diesel consuming 5.3 litres/100km on the official test (combined cycle).
The same engine powers the all-wheel drive xDrive 25d. It provides perfectly acceptable performance for most drivers in most driving conditions.
Nevertheless, the most popular engine in an X5 is the bigger and more powerful 3.0-litre diesel fitted to the xDrive 30d. It offers muscular acceleration from low speeds, and effortless overtaking and towing. And it uses only slightly more fuel on the official test, at 5.9 litres/100km. (Like most cars, the xDrive 30d needs more fuel in the real world: expect 8 or 9 litres/100km.)
A still more powerful, and slightly thirstier, variant of this 3.0-litre diesel is offered in the xDrive 40d.
If you are one of the few people who want even more performance from a diesel X5, you may be interested in the X5 M 50d. Its 3.0-litre engine is boosted by no fewer than three turbochargers, delivering stupendous performance and an engaging sound (unusual for a diesel), while containing fuel use to just 6.6 litres/100km.
One reason you might not want a diesel X5 is that you don’t want to deal with oily diesel fuel and greasy diesel fuel pumps. For you, the X5 is offered with three petrol engines.
The least costly petrol X5 is the xDrive 35i, whose 3.0-litre turbocharged six cylinder brings you fine, silky smooth performance. Ultimately an xDrive 35i will be slightly quicker than an xDrive 30d, with the greater willingness to spin hard that is typical of a petrol engine, but with a little less grunt for towing.
Then there is the xDrive 50i, powered by a 4.4-litre V8 engine running two turbochargers. It’s a serious performance vehicle, and is thirsty in day to day running.
The most expensive – and quickest – model in the X5 range is the X5 M. It also uses a 4.4-litre, twin-turbo, V8 petrol engine, but one that is significantly reworked and upgraded to deliver extremely high performance and an equally eye-widening fuel bill. On the official test it consumes 11 litres/100km, but it’s easy to use twice as much fuel with enthusiastic driving.
If you expect you will use your X5 largely for short trips around town, and you need only five seats, you might have good reason to bypass all of the conventional diesel and petrol engines and choose instead the petrol-electric plug-in hybrid X5, the xDrive 40e. For round trips shorter than about 25km you can drive an xDrive 40e using no petrol at all, relying instead on its electric motor and battery, which you can recharge fully at home in about five hours. On long trips in the country, however, where you will be driving mainly on its paired 2.0-litre, four-cylinder, turbo petrol engine, it is likely that fuel use will greatly exceed the 3.3 litres/100km attributed to this car from the official test: expect to use more like 10 litres/100km. Performance will be comparable with the xDrive 30d and xDrive 35i.