The revised BMW 6-Series range of Coupe and Convertible models goes on sale in the UK tomorrow.

Amongst the changes is the adoption of the weight and energy saving EfficientDynamics elements.

There are also detailed styling and design changes inside and out. Prices range from £49,300 up to £88,225 for the M6, 507bhp, Convertible model.

The 6-Series accounts for around 2,000 sales in the UK each year, 60 per cent of them Coupe models and 90 per cent of customers, mainly retail buyers or business users-chooser customers, go for the Sport specification.

However there is now the opportunity to grow 6-Series sales in this country for one unusual reason. BMW are introducing with the revised range, 635d Coupe and Convertible models, the world’s first diesel powered luxury 2+2 Grand Tourers. 

Around 60 per cent of 6-Series customers are expected to opt for these diesel powered models. The Coupe 635d is priced at £53,910 and £56,110 with Sport specification. The Convertible models are priced at £59,600 and £61,800 for the Sport version.

The twin turbocharged 3.0-litre diesel engine with 286bhp and 580Nm of torque at 1,750rpm has previously been seen in the BMW 335d and 535d.

The aim is to make the new 635d the ultimate cross-country Grand Tourer delivering rapid acceleration, consistent high speed, the best possible fuel consumption and low emissions. 

Over 600 miles on a tank full of diesel is impressive. Both models have a top speed limited to 155mph with the Coupe covering 0-62mph in 6.3 seconds and the Convertible in 6.6 seconds.

Average fuel consumption is 40.9mpg for the Coupe and 39.2mpg for the Convertible. The Coupe’s CO₂ emissions are 183g/km putting it in Band E £165 for vehicle road tax and the Convertible, with 190g/km, in Band F at £205.

Imposing to look at with its wider stance and seemingly longer length, all down to new styling tweaks, the 635d with the smooth, quiet and responsive twin turbodiesel engine and six-speed automatic transmission is probably the best Grand Tourer on the market. It is roomy too for four adults.

My test car, the 635d Sport Convertible priced at £61,800, returned 34.4mpg. The huge 580Nm of torque available at such a low engine speed makes acceleration instant when need for over taking slower traffic in the minimum of time and distance.

The installation is so refined you really do not know it is a diesel engine.

It is simply stunning and it will give other high powered petrol engined Grand Tourers a real run for their money, especially as it means less visits to a filling station on long journeys.