To some 'the world's lightest six cylinder engine' will figure in their buying decisions about as prominently as 'the world's most durable suspension turrets' or 'the most aerodynamic cup holder in automotive history'. It just doesn't seem that significant, especially in a car as luxuriously stuffed as BMW's 630i. But hang on a minute. With less weight hanging out over the nose, there are all sorts of handling benefits. This is BMW, remember, alleged purveyors of 'The Ultimate Driving Machine'.

The 630i Coupe and Convertible feature a 3.0-litre Valvetronic engine with technology that does away with conventional throttle butterflies in favour of a complex electrically-powered valve lifting system. Constructed from an aluminium and magnesium composite, this engine sits tucked well back in the car's cavernous engine bay and gives the 630i excellent weight distribution. Less weight also equates to better performance, more agile handling and lower fuel consumption and emissions.

Despite the modest cubic capacity, this engine punches well above its weight, knocking out 272bhp. On the road this translates into a surprising amount of heft. The sprint to 60mph from rest will disappear in around six and a half seconds. Specify the optional automatic gearboxes and you'll add a couple of tenths to these sprint figures. All versions run into BMW's self-imposed electronic limiter at 155mph with plenty to spare yet thanks to a recent programme of what BMW call 'EfficientDynamics', the 630i can still manage a combined fuel economy figure of 35.8mpg in Coupe form and 34.0mpg if you go for the drop top.

The 630i is tricky to distinguish from its 635d 3.0 diesel or 650i petrol V8 siblings. Drive one over a set of scales and the 130kg weight saving over the petrol V8 would become apparent but otherwise you'd have to rely on the buyer not having ticked the 'badge delete' box on the order form. Prices start at £49,300 for the Coupe and £54,945 for the Convertible and there's a choice of standard or Sport models in each case.

"Star quality is a tricky thing to define but the 6 Series just has it"

This is the facelifted 6-Series but you'd really have to eyeball one parked alongside the original car to pinpoint the changes. For the record, the headlamps have the LED technology that is so popular amongst the premium marques at the moment. It takes the form of a thin row of lights above the main projectors. More obvious is the redesigned front valance that accommodates differently shaped air intakes and at the back the bumper has been tweaked it increase the impression of width. Other than that, the grille is fractionally larger and the rear light clusters have been tweaked.

Time was when entry-level BMWs didn't come with too many buttons to press, owners being confronted with a dazzling array of plastic switch blanks to remind them of their place in the hierarchy. Fortunately these days have long gone and the 630i features a whole host of standard equipment. Leather trim makes the team sheet as do a whole host of standard safety features such as Dynamic Stability Contol, Dynamic Traction Control and Dynamic Brake Control. If, at this stage, you feel your 630i is lacking its full quota of dynamism, you can even opt for Dynamic Drive. Active Steering is also offered.

Dynamic Driving Control is a function very similar to the 'Sport' mode on M3 and M5 models. Press a button on the centre console and this sharpens up throttle reaction as well as generating a little more feel from the steering system. When allied to the SMG or Steptronic gearboxes, DDC also shifts gears at higher revs, switching ratios in just 150 milliseconds. Whichever system you choose, you'll be amazed at the sheer grip generated by the roadroller Bridgestone Potenza tyres. That said, the 6 Series feels just that little bit too big to be a truly effective cross-country tool. On sweeping A-roads, we've always found 6 Series models to be magnificent and the 630i should prove to be no different. According to BMW's figures, third gear is capable of reaching over 100mph and the engine's gutsy 332lb/ft of torque should make it almost unnecessary to resort to stirring the box.

An option many customers will choose is BMW's Dynamic Drive. This automatically builds up counter forces on the car's anti-roll bars and as such, virtually eliminates any body roll when cornering. After trying a car with Dynamic Drive and another without it, it's an option worth pursuing if you plan to enjoy serious lateral g-forces. Another interesting option BMW offer is Active Steering, a system that debuted to mixed reaction on the latest 5 Series. This dramatically varies the steering ratio according to speed. At low speeds, you'll often need little more than a quarter of a turn on the wheel to effect a 90-degree turn. It's easy to be caught out when decelerating from a motorway into the tight car park of a service area by Active Steering but it's probably something to which you'll grow accustomed. Customer take-up of the option on 5 Series models has outstripped BMW's most optimistic estimates. There's also Adaptive Headlights which turn through corners, a Head-up Display which projects vital information onto a section of the windscreen and Active Cruise Control that uses radar to maintain a safe distance to the vehicle in front.

Even with none of these options selected, the 6 Series is still a very nice place to do business. Core driving functions are located in or around the steering wheel and a simplified version of the iDrive system offers a still enormous amount of driver control with just a few nudges, taps and twists of the serrated metal mouse. The dashboard design is otherwise rather low key, the analogue dials being rather disappointingly small.

Still, it's tough to be overly critical of what is one of the strongest models in BMW's entire line up. The 630i can make the rest of the 6 Series range look a bit overblown. Although this could prove a headache for BMW, it's great news for us.

TOP 5 6 SERIES DEALS

The results below show the top 6 SERIES deals on buyacar

	BMW 6 Series 630i Sport 2dr [272] Coupe
	ETR	Mthly	Saving £2,724	Price £48,781
	BMW 6 Series 630i 2dr [272] Coupe
	ETR	Mthly	Saving £2,603	Price £47,187
	BMW 6 Series 630i 2dr Auto [272] Coupe
	ETR	Mthly	Saving £2,714	Price £48,606
	BMW 6 Series 630i Sport 2dr Auto [272] Coupe
	ETR	Mthly	Saving £2,870	Price £50,650
	BMW 6 Series 630i 2dr [272] Convertible
	ETR	Mthly	Saving £2,968	Price £51,982