BMW ActiveHybrid 5

Engine: 3.0-litre in-line six-cylinder petrol engine paired with electric motor
Transmission: eight-speed automatic
Power: 306 PS at 5,800 rpm + 40kW (electric motor)
Torque: 400 Nm between 1,200 and 4,000 rpm
Fuel consumption (combined cycle): 44.1 mpg
CO2 emissions: 149 g/km
Top speed: 155 mph (artificially limited)
Acceleration (0-62 mph): 5.9 seconds
Price: £46,855

If you’re a competitor or an official at this year’s London Olympics, there’s a good chance you’ll be ferried around at some stage in a BMW 5-Series. BMW is the Games’ Official Automotive Partner and is providing 727 5s as part of a 4,000-strong fleet of cars that will provide transport within and between venues for the busy people who are expected to make the whole thing work.

London 2012 aims to be the first sustainable Games and LOCOG, the London organising committee, set BMW tough fuel efficiency and CO2 emissions targets for the fleet of 62.4mpg and 120g/km. In fact, the company has been able to better these benchmarks and the Olympic cars will have an average fuel consumption in official tests of 64.5mpg and CO2 emissions of 116g/km; that’s roughly on a par with a Ford Ka, even though the fleet will have an average power output of 157bhp and contain large numbers of big cars such as the 5-Series and even some SUVs.

The bulk of the 5s - 707 of the 727 - will be the highly economical 520d EfficientDynamics, which, with its turbocharged two-litre diesel engine, emits just 119g/km of CO2 and has an official combined cycle fuel consumption of 62.8mpg, which probably makes it just about the most efficient car in its bracket. Twenty, though, will be petrol-electric hybrids in the form of the ActiveHybrid 5 model, which emits 149g/km of CO2 and can travel 44.1 miles on a single gallon, at least according official tests.

At first sight, it’s difficult to see the point of the ActiveHybrid 5 – its emissions figures and fuel consumption are respectable for a big car, but don’t come close to matching those of its diesel sister. Throw in a list price of £46,885 compared with the £30,435 BMW is charging for the diesel and on paper at least, it’s hard to see the purpose of the hybrid, except perhaps as a token bit of greenwashing brochureware for diesel-averse American buyers.

But get the ActiveHybrid 5 out on the road and a completely different picture emerges. BMW’s four-cylinder diesel, for all its impressive efficiency, is a slightly rough old thing compared with the best engines of its type these days but the hybrid, with its outstandingly smooth and eager in-line six cylinder petrol engine, supported by silent and torquey electric power, is in a completely different class for refinement and performance. The 520d EfficientDynamics gets from rest to 62mph in 7.9 seconds before topping out at 141mph – highly respectable figures but no match for the hybrid, which can accelerate to 62mph in 5.9 seconds on the way to an artificially limited maximum of 155mph. Seen in that light, the CO2 and fuel consumption penalty associated with the hybrid actually looks pretty good. The role of the ActiveHybrid 5, therefore, is to provide an efficient alternative to BMW’s big petrol-only cars such as the 535i (the hybrid emits 19 per cent less CO2) without any loss of driving pleasure. In fact, the hybrid drivetrain may just be the saviour of the company’s glorious six-cylinder petrol engines which provided the backbone of the BMW range and shaped the company’s reputation for so long.

One notable aspect of the ActiveHybrid 5’s behaviour is that it doesn’t actually feel very “hybridy” – although that may be because we have been conditioned to expect hybrids to be slow and not much fun by the Prius and other models from Toyota, the pioneer in the field, which have sluggish, moaning CVT-based drivetrains. BMW says that the ActiveHybrid 5 will go for up to 2.4 miles in electric-only mode but in practice, even when you accelerate very gently from rest, the petrol engine seems to cut in at about 18 mph, although it comes in so smoothly and quietly, it’s often the rev counter rather the noise emanating from under the bonnet that gives the game away. For the most part, though, the ActiveHybrid 5 just feels like a good big-engined petrol BMW, which is a very good thing indeed.