In-depth Reviews

BMW 8 Series coupe - MPG, running costs & CO2

BMW 8 Series fuel consumption isn't excessive, but general running costs will still be high

Carbuyer Rating

4.0 out of 5

MPG, running costs & CO2 Rating

3.0 out of 5

The BMW 8 Series steals a march on several close rivals by being available with diesel power. Those who expect to cover a high annual mileage will welcome the 840d's claimed fuel economy, but that doesn't mean any 8 Series will be anything but costly to run in real terms.

It's too early to predict how much a three-year old 8 Series will be worth when it comes time to sell, but even if the residuals are strong, buyers will have lost a significant amount of money to depreciation. There's little reason to think the BMW will perform any less well here than the Mercedes S500 coupe, though, which CAP – the independent car valuation specialist – says can retain 45% of its original purchase cost after three years and 36,000 miles.

BMW 8 Series MPG & CO2

BMW claims that the M850i can return 25.2mpg overall, although we expect that figure to drop markedly if you make frequent use of all the engine’s power. It emits a huge 255g/km of CO2, so those lucky enough to claim one for a company car shouldn’t be surprised by its top-rung Benefit-in-Kind (BiK) tax liability.

The cheaper 840i petrol engine is the latest addition to the range, and BMW says 33.6mpg is possible in normal driving. It’s actually ever-so-slightly more frugal than the BMW 2 Series M240i coupe, which has the same amount of power.

For the diesel 840d, BMW makes the more palatable claim of 40.4mpg, which is close to what the BMW 7 Series manages with the same 3.0-litre engine. Emissions of 183g/km of CO2 is far less than the M850i produces, but non-compliance to Real-time Driving Emissions 2 (RDE2) test standards still puts the 840d in the highest 37% BiK bracket. Better news is its realistic 500-mile range on a full tank of diesel.

Insurance groups

Both the BMW 840d and M850i are rated in the highest group 50 insurance classification as decided by the Association of British Insurers (ABI), while the 840i will bring slightly lower premiums as it’s in group 45. The majority of rivals carry a similarly high insurance group rating, and we always suggest you seek an insurance quote prior to buying.


BMW provides a three-year/unlimited mileage warranty on every new car it sells in the UK. This matches the policy of Mercedes and beats Audi, which limits total mileage to 60,000 miles. On its expiry, you can extend your BMW warranty a year at a time, although certain exclusions apply.


BMWs use a condition-based system with variable service intervals controlled by wear and oil-quality sensors. You'll almost certainly need to take your 8 Series to a workshop at least every other year, and while an oil change might not cost the Earth, consumable parts like tyres and brakes will be expensive.

Your BMW dealer can set up a service contract to suit how you expect to use your car.

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