Parkers overall rating: 4.1 out of 5 4.1

Miles per pound (mpp) Miles per pound (mpp)

Petrol engines 4.1 - 5.7 mpp
Diesel engines 6.5 - 7.2 mpp
Low figures relate to the least economical version; high to the most economical. Based on WLTP combined fuel economy for versions of this car made since September 2017 only, and typical current fuel or electricity costs.

Fuel economy

Petrol engines 24.4 - 33.6 mpg
Diesel engines 39.2 - 43.5 mpg
  • No BMW 8 Series Convertible model is cheap to run
  • Expect expensive tyres and other consumables
  • The diesel model consumes considerably less fuel

Whether you pick petrol or diesel it’s fair to say that the BMW 8 Series Convertible will cost you more to run than a 1 Series Hatchback, in terms of fuel, insurance, consumables and servicing. The diesel 840d is the clear winner when it comes to fuel consumption, promising between 38.7-39.8mpg to the 840’s 32.5-33.2mpg and the M850i’s 24.6-24.8mpg.

These figures will obviously dip with sporty driving but we’d expect the diesel to offer reasonable economy even when you choose to exploit its full potential. We rarely reached above an indicated 20mpg during our time with the M850i – with figures typically in the late teens. This is despite having stop-start and an active front grille that closed to help the convertible slip through the air that little more.

BMW M850i Convertible exhaust 2019

The M8 Competition is quoted to achieve a slightly higher 25.2mpg, with CO2 emissions of 241-246g/km. As an indication of a worst-case scenario figure, we saw an indicated 12.6mpg with the Coupe version after a hard day’s driving.

With a fuel tank capacity of 68 litres, this could mean you won’t see over 400 miles per fill-up, even if you get close to the official figures. You’d imagine a large, heavy convertible like the BMW 8 Series to produce a substantial amount of CO2 and in the case of the V8 petrol you’d be broadly correct – the M850i clocks in with at 228-231g/km.

In comparison, the entry-level 840i emits between 168-170g/k. In the case of the diesel-powered 840d, things are considerably better, with 161-165g/km of CO2, despite that punchy 0-62mph time and hefty torque figure.


  • New model with new engines
  • BMW has a strong record for reliability
  • Shouldn’t need to worry much

Given the BMW 8 Series Convertible’s newness it’s hard to say exactly how well it will perform in this area but given the prolific use of engineering and technology from throughout the BMW parts catalogue, you hope you shouldn’t have much cause for concern.

However, it's worth noting that in the 2018 JD Power Vehicle Dependancy Survey, BMW had real problems, with 192 problems per 100 vehicles studied. And yes, it was plumb last in the list that was topped by Hyundai, which scored 78.

BMW 8 Series rear badge 2019

Ongoing running costs

Road tax (12 months) £490
Insurance group 47 - 50
How much is it to insure?