BOATS, horse floats and palatial caravans owned by Mercedes GL customers could be about to travel a fair bit faster thanks to the addition of a twin-turbo V8 diesel engine as part of an updated range.

Already on offer for some time overseas, where it has served in several vehicles including the S-Class limo, the 450 CDI engine has been added to the Australian range following requests from GL customers who use their vehicle for towing.

It is a 4.0-litre V8 direct injection diesel with a turbocharger on each cylinder bank that manages to generate a healthy 225kW and some 700Nm of pony-pulling torque that is available from 2800rpm to 4800rpm.

The actual towing capacity of the GL450, with a braked trailer, remains at a respectable 3045kg, but is able to lug the load a lot easier.

It is hardly a green engine, recording an official average fuel economy of 11.8 litres per 100km, but it is better than the petrol V8 GL500, which uses 13.5L/100km. Similarly, emissions run only slightly lower at 313g/km for the diesel V8 against 322g/km for the petrol.

The smaller 3.0-litre V6 diesel in the GL350 has been given an upgrade. This direct injection single turbo engine now generates 195kW and 620Nm of torque – not far short of the big V8 while returning 9.2L/100km and 242g/km.

The 5.5-litre naturally aspirated petrol V8 that powers the GL500 remains unchanged, producing 285kW and 530Nm.

All GL engines are paired to a seven-speed torque convertor transmission, which feeds all four wheels.

The addition of the diesel V8 and the upgraded V6 diesel are the last major changes before the next generation version of the seven-seat SUV arrives next year.

Mercedes has slotted the V8 diesel GL450 in just below the V8 petrol GL500 with a price of $169,800 for the single Luxury model.

The price of the other GL models has risen by close to $2000, with the GL500 Luxury costing $173,200 and the GL350 V6 diesel now $119,270 and the GL350 Luxury up to $173,200.

Mercedes upgraded the GL range last year, bringing a fresh new front design with a new grille, front bumper, LED daytime running lights, a new-look rear bumper and LED tail-lights.

The GL450 comes with the same specification as the GL350 Luxury but adds massive 21-inch AMG alloy wheels, a sunroof, keyless entry and start, front luxury seats with heating and ventilation, heated second row of seats, Nappa leather trim and a TV tuner.