Mercedes GLS review - MPG, CO2 and running costs

There’s only so much a combustion engine – no matter how efficient – can do to offset the need to haul around a 2.5-tonne SUV. So while the 3.0-litre V6 diesel is a capable unit, at best it achieves 30.7mpg in official WLTP tests. Spend time driving in town and that number is likely to drop quite significantly. Despite the relative thirst, an enormous 90-litre fuel tank means that, should you match the official economy figures, the GLS will cover about 600 miles on a tank.

The Mercedes-AMG GLS 63, trading economy for extra performance, is only able to achieve a maximum 22.1mpg.

Prices for the diesel-powered GLS start from just over £75,000 and climb to around £92,000 before options. You'll need deeper pockets in order to be able to climb into one of the AMG versions, with the top-of-the-range GLS 63 Night Edition Executive version priced at an eye-watering £128,285.

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Insurance groups

With such a hefty price tag, insurance costs aren’t likely to be cheap. Groupings for the GLE head right to the top of the 50 classifications available, so a big budget will be needed beyond the initial purchase price.

Depreciation

Depending on the trim level, the GLS is predicted to hold between 43 and 49% of its value over three years and 36,000 miles. That’s some way behind the BMW X7, which retains up to 56% over the same period.