THE third generation of Mercedes-Benz's big luxury 4x4 has moved up a notch and is ready to take on the latest from the likes of Land Rover and BMW.

It won't be on sale in the UK until next April but an early test drive impressed with the model's new looks, improved engines and most of all its stunning off-road capability.

The big, five-seater Merc has also been given a much needed new-look interior which includes high quality wood, leather and aluminium finish.

The new M-Class is also slightly wider, longer and higher than the previous model which gives driver and passengers better leg, shoulder and headroom.

A new exterior design has given the German motor a sportier look with a sloping roof line to the rear plus large roof spoiler and two-part rear light unit with LEDs.

The front is dominated by the now classic Mercedes star in the centre of the wide three-bar grille.

Alloy wheel choices are 17 or 20-inches and 21 for the hugely powerful AMG version..

Mercedes claims that the new M-Class is the most aerodynamically efficient SUV in its class and at high speed on the German autobahns very little wind noise was detected and there was also very little intrusive engine or road noise.

The new engine line-up at launch includes the 250 BlueTEC which is claimed will return 44.8 mpg on average. There is also the 350 BlueTEC at 39.2 mpg which is a 20.6 per cent improvement on the outgoing engines.

Exhaust emissions have also been slashed with the ML250 now rated at 158g/km - a critical figure below the 160g/km tax threshold for business users.

The ML350 comes in at 179g/km - not quite as clean but still way down on the 235g/km of the previous generation and a huge achievement for a vehicle of such size.

Even the massively powerful 5.5-litre V8 biturbo AMG 63 is claimed to average 24 mpg.

Despite the tw-tonne-plus weight of the big 4x4 all versions will easily hit 62 mph in well under 10 seconds.

Each version of the new M-Class features a new 7G-Tronic Plus 7-speed automatic transmission which also incorporates a new stop/start system which I found cut in very smoothly from standstill.

Under normal road conditions the M-Class is as solid as a rock and soaks up any rough surfaces giving a soft comfortable ride.

Also new to the M-Class is Active Curve System. This uses active anti-roll bars on the front and rear axles, which it controls irrespective of lateral acceleration, speed or suspension settings and on tight bends it cuts out almost all body roll.

The off-road capability is outstanding, although I doubt that few owners will be tempted to put their luxury motor through the mill.

But on a disused quarry used by many motor manufacturers to test off-roaders I was mightily impressed.

Helped by the tightest turning circle in its segment, the new M-Class easily conquered the toughest of tests including a frightening 80 per cent downhill drop and 35 degree side slopes.

Start-off assist and the hill hold function are further features helping the driver to pull away on a slope. Downhill speed regulation, or DSR, enables the M-Class to maintain automatically the speed set via the cruise control lever.

Both active safety and driver-fitness safety in the new M-Class are improved by assistance systems that will already be familiar, primarily from the Mercedes S and E-Class.

The standard equipment package includes the drowsiness detection system ATTENTION ASSIST, the anticipatory safety system PRE-SAFE® and a tyre pressure loss warning system, as well as adaptive brake lights and Brake Assist (BAS). Active assistance systems such as Active Lane Keeping Assist and Active Blind Spot Assist are available as additional equipment options:

The new M-Class comes as standard with the Audio 20 CD system, which comprises a radio with twin-tuner, a colour display with a six-inch screen, an MP3-compatible CD player, a USB interface.

The list of standard equipment on the new M-Class is huge, and includes skid control, heated seats, heated mirrors, rain sensors, automatic wipers, daytime running lights, tyre pressure warning system, cruise control, heat-insulating glass and a Harman Kardon Logic surround sound system with 12-channel amplifier pumping out a total of 830 Watts.

Prices in the UK have yet to be announced but will probably be slightly up on the present M-Class which starts at £42,225.