BMW 8 Series review - MPG, CO2 and running costs

Tiresome though the news may be, if you’re forced to factor running costs into your new car purchase, it’s highly unlikely the M850i is the right model for you. BMW says it will cover up to 26.9mpg on the (WLTP test) combined cycle and we easily reached this number during a motorway test drive, but if you tap into its phenomenal performance too often you’ll see the MPG figure will drop like a stone.

Equally, the 239g/km of CO2 emitted under test conditions is unlikely to match real world use, but at least that won’t cost anything more from a financial perspective. The car is in the maximum Benefit-in-Kind bracket, too, so you’ll be whacked by the tax man if you run an M850i on the company, although it’s a similar story for any high-performance company car – unless it’s a hybrid or electric vehicle.

The 840i petrol model manages up to 33.6mpg with CO2 emissions of 190g/km, while if you want to track down a used 840d diesel version then you'll benefit from fuel economy of around 44mpg.

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Insurance groups

The Association of British Insurers has assessed both the new 8 Series models as insurance group 50, which means sky-high premiums for anyone not on a multi-car company-type policy, or on very good terms with their broker. It’s no surprise though, as all high performance and luxury cars are expensive to cover.

Depreciation

Initial residual values for the 8 Series were strong, although this has waned slightly over time, with expert data suggesting the M models will only hold onto an average value of around 45 per cent after a three-year/36,000-mile ownership period. The 840i fares a little better on 51 per cent.

Buyers should be wary of ticking the expensive Ultimate Pack option. It costs around £15,000 and, although it brings many extra features, it does nothing for long-term values.