It probably won’t come as a surprise that Mercedes-Benz G-Class G63 AMG running costs will be high. It is, after all, a premium high-performance off-roader.

Its 5.5-litre twin-turbocharged V8 is optimistically claimed to average 20.5mpg but it’s more likely you’ll average between 10-15mpg in daily use.

That might sound poor, given the advanced AMG engine and the car’s 7-speed transmission, but the G63 AMG weighs 2,550kg and has the aerodynamics of a truck. Consequently the engine has to work quite hard to keep the G-Class moving, harming its economy.

Unfortunately there are plenty of big bills waiting for you elsewhere. Road tax is costly, servicing and repair bills won’t be cheap and replacement tyres and braking components will prove alarmingly expensive.

If you’re looking at buying an older example, it’s worth taking into account the fact that as the car ages it could become increasingly difficult to maintain and repair. Even a simple fault could require substantial disassembly of the G63 AMG, racking up substantial labour charges.

On the plus side, major mechanical issues should be few and far between.

It probably doesn’t come as a great surprise that the Mercedes-Benz G-Class G63 AMG’s green credentials aren’t fantastic.

Even though the engine features a host of advanced technology, including start/stop, the G63 AMG’s emissions are rated at a substantial 322g/km of CO2.

That means you’ll be paying a considerable amount for road tax each year, as well as being hit with a large initial showroom tax bill.

Fuel economy won’t impress either, with the G63 AMG being claimed to average 20.5mpg. Its real-world economy will most likely be considerably less than that.

You might think that’s par for the course for a powerful off-roader but alternatives like the Porsche Cayenne Turbo are much cleaner. The Porsche is also faster, more efficient, considerably more competent on the road and far less costly.

Like the G-Class, however, one positive aspect of the G63 AMG is that it’ll probably last for a long time. That’ll go some way to minimising its impact on the environment.

Mercedes-Benz G-Class G63 AMG reliability should be good. Many of the components used are well proven and the G-Class is renowned worldwide for its longevity.

Not many G63 AMGs will be driven regularly off-road. Many will, for the most part, live cosseted lives and not cover many miles. As a result they will last for a long time and shouldn’t suffer from any major issues.

One thing that’s worth bearing in mind is that the G63 AMG is a complicated off-roader that’s very tightly packaged. As it gets older it may become increasingly expensive and difficult to maintain, particularly compared to older versions of the G-Class.