INITIALLY it seemed inappropriate to test a giant GL450 in the middle of Melbourne, in treacle-like traffic, but it was probably quite suitable.

This is, after all, a seven-seat people-mover and most will spend their time on the way to schools and offices in the city or surrounding suburbs.

Mercedes has three people-movers in the R-Class, GL and the van-based Viano.

The Viano is the most sensible of the trio but will not pass the cool test for many Mercedes customers, the high-riding R-Class wagon sits in-between given it is a little more sensible than the Viano but not quite as cool as the GL, which has rugged SUV styling.

The huge GL in 450 CDI form weighs an incredible 2585kg, which means powerful engines are needed to get it up and moving.

When customers want to tow something equally heavy or even heavier (up to 3405kg), there is a lot of work for the engine to do, which is where the twin-turbo diesel V8 comes in. With 700Nm of torque, the engine is able to overcome great weight.

We were unable to tow anything during our urban test, but it was still quite easy to tell how well the GL450 will tow. Having a heavy vehicle is good for towing and the fact it is also huge (it measures 5099mm from nose to tail) and has a long wheelbase aids stability.

The tremendous torque of the V8 engine complements these other elements to create a car that should be able to easily handle a giant boat or a horse float. It will also ensure the driver has no problem accelerating quickly in the urban environment. With only three people on board and no luggage, the GL450 accelerated with amazing force on the few occasions we had a gap and the chance to press the throttle.

The big V8 is not the most refined diesel on the market but you tend to overlook this fact given the performance it offers. It has an interesting engine note, sounding more like a regular V8 under acceleration than a diesel. It is a generally enjoyable sound, especially given it accompanies rapid acceleration.

The fuel economy on our test drive was not good, with heavy traffic blowing out the number. The indicated fuel consumption average of 15.8L/100km was not pretty, but I am tipping it is still a lot better than the V8 petrol version would perform in the same circumstance.

We were only able to test the V8 diesel GL, but I would recommend potential customers also test drive the newly revised V6 diesel, which has only 80Nm less torque and 30kW less power, and uses less fuel.

A brief dash on the highway revealed the big V8 diesel is great for cruising. Sitting at 100km/h it ticked over at just 1500rpm.

The seven-speed automatic transmission works well. It doesn’t need to make many down-changes given the engine’s great torque and any changes it does make are smooth.

As a city vehicle, the GL is ordinary. It is scary to think that some customers would purchase this vehicle for primary use in The Big Smoke.

The problem is its size and weight. Driving around tight city and narrow suburban streets reminds me of a mahout leading an elephant in central Bangkok.

It is comfortable on the whole, although cornering could bring on sea-sickness.

The single Luxury model is loaded with the kind of gear you expect for this kind of money. For example, you don’t have to lean in and pull up the third row of seats, you simply press a button and they go up or down.

The interior has a classy mix of black leather and woodgrain that suggests you could be riding in one of Mercedes’ high-end sedans or coupes.