IT'S not hard to distinguish the distinctive rumble of a V8 engine beneath the bonnet, or so I thought before I got behind the wheel of Audi's new sporting S6 saloon.

For while the latest generation of the S6 sounds like a eight cylinder petrol engine it's actually powered by a V6, and a V6 diesel at that.

For the first time the S6 models, the new version of which went on sale this summer, are available with TDI power boosted by a 48-volt mild hybrid drivetrain.

The result is a car which - if you take a test drive - will go straight to the top of your "must have" list.

For the S6 delivers on every front. It's fast, it's incredibly torquey (with 700 newton-metres of torque), it's comfortable and it's classy.

The 3.0-litre engine boasts 350bhp which sees it hitting 62 miles per hour in just five seconds on its way to a top speed of 155mph.

But the beauty of this car - apart from the V8 sound - is just how flexible and responsive it is to drive. Diesel might be out of favour at present but after a week with the S6 I found it impossible to have any negative thoughts about this car.

The combination of diesel and electric means you get spine tingling performance but with sensible economy.

Audi claims the car will average a whisker over 36 miles per gallon but on both of two long distance journeys I recorded a very impressive 50mpg and that sort of economy combined with the performance the S6 delivers is what will make people buy.

With this car the power is always there instantly when you need it no matter what speed you are doing thanks in part to the absence of turbo lag, due to new dual supercharging technology.

The spontaneous response and impressive pulling power when accelerating or overtaking makes this a real driver's car and is guaranteed to put a smile on your face.

This is a classy piece of kit, characterized by its striking, distinctive design. With, in the case of the car driven here, 21-inch alloys (an extra £1,550), quad exhaust pipes, heavily tinted privacy glass and an aggressive face it looks the part while still being understated.

There are distinctive S trim elements in dark chrome and aluminium on the radiator grille, the exterior mirrors and the rear diffuser marking it out from the standard A6 on which its based.

Inside too there's an executive feel all the way, with diamond patterned Valconna electrically adjustable leather seats, a piano black facia and Audi's virtual cockpit with a 12.3-inch display - which allows you to change the configuration of the dials.

There's plenty of legroom for rear seat passengers to stretch out in comfort and there's a very generous 530-litre boot.