SPY PICS: Butch Mercedes G-Class lightens up

Mercedes-Benz has been caught testing the latest version of the oldest vehicle it makes, the G-Class, or G-wagen.

Set to go on sale in 2018, the updates of the tough old 4x4 (that first went on sale back in 1979) are thought to include a wider body and track, compared to the current car.

If true, this could signal the biggest change to the G-Class since the road-going body-on-frame G-wagen was introduced 38-years ago.

The wide body, claimed to be as much as 100mm wider than the existing car, should provide more interior and shoulder room for the boxy SUV's no doubt very wealthy owners

Other changes include a completely overhauled cabin that will introduce the firm's latest infotainment system.

To help cut fuel use, additional lightweight materials like carbon-fibre are expected to be used in the G-Wagen's construction, with some claiming that engineers have been tasked with cutting at least 200kg from the current car's 2850kg kerbweight.

Other fuel-saving tech will see electric power steering adopted for the first time and all versions, bar the range-topping G65 AMG, will come with the firm's latest nine-speed automatic.

Safety equipment will also improve on the new model, with new features like autonomous emergency braking and lane-keep assist set to become standard. The G-wagen could also potentially come with a development of the E-Class' semi-autonomous cruise control.

When it goes on sale in two years' time we expect the G-Class to come with a 3.0-litre V6 turbo-diesel and a development of the mighty AMG GT's 4.0-litre V8 twin-turbo that will power the G500 and G63 AMG.

At the top of the G-wagen tree, we expect the G65 AMG to keep its twin-turbo V12 and possibly run a heavily modified version of the current 6.0-litre unit.

Prohibitive costs of development is likely to rule out any plug-in hybrid version.

Like the current car, expect the wider more spacious G-Class to come priced around $200,000 for a G500.