BMW has introduced a new engine to its 6 coupe and convertible range, and has made a number of changes to make the cars less environmentally damaging.
The 6 has also been given a mild face-lift, with small cosmetic changes to the exterior.
The biggest change is the introduction of BMW's twin-turbo 282bhp 3.0-litre diesel. This powers the 6 to 62mph in 6.3sec, and on to a limited top speed of 155mph.
Average fuel economy is 40.9mpg (coupe) and 39.2mpg (convertible), with carbon dioxide emissions of 183g/km (190g/km convertible).
BMW has been making efforts to improve the average carbon dioxide emissions of its entire fleet to meet stringent new EU targets, and the 6 is the latest to benefit from these improvements.
Topping the list is regenerative braking, which uses the brakes to charge the battery.
BMW has also introduced mechanisms that prevent energy waste - for example, the air-conditioning compressor can be disconnected from the drivetrain to stop it creating drag on the engine.
Using these technologies and high-precision fuel-injection techniques, it means BMW has been able to reduce fuel consumption and carbon dioxide emissions.
For example, the 630i coupe has improved by 4.4mpg to 35.8mpg and its emissions drop from 216g/km to 188g/km. Automatic versions do better, up from 29.7mpg to 36.7mpg and emissions falling from 238g/km to 184g/km.
Convertible 630i cars now manage 34mpg, up from 29.4mpg, and emissions drop from 229g/km to 198g/km.
The 650i coupes, with their 4.8-litre V8 engines, have also been made slightly more efficient. Fuel economy is better by 2% at 24.1mpg (a 7% improvement in the convertible, up to 22.4mpg), and carbon emissions are cut from 310g/km to 299g/km.
As well as the environmental improvements, there are a number of cosmetic alterations. There's a revised headlight arrangement featuring clear lenses and LED technology, and a new front valance.
There's also a differently shaped front air intake and a larger front grille, while there are new alloy wheel designs and a third high-level brake light on the boot lid.
Active head restraints are also now standard across the range.
The new 6 goes on sale in the UK in October.
630i coupe £49,300
630i Sport Coupe £51,500
635d Coupe £53,910
635d Sport Coupe £56,110
650i Coupe £55,895
635d Sport Coupe £57,745
630i Convertible £54,945
630i Sport Convertible £57,145
635d Convertible £59,600
635d Sport Convertible £61,800
650i Convertible £61,365
635d Sport Convertible £63,215
Our reviews are based on hard data and thorough testing in the real world.
Up to the minute news from around the globe