20 MPG combined won’t win any fuel efficiency awards, but for the 2020 BMW M850i xDrive Convertible with its snarling 4.4L V8, it’s almost beside the point. This isn’t a car for budget-conscious commuters; it’s a statement, a weekend escape, and a provider of effortless power designed for those who prioritize performance and luxury. The M850i Convertible is about the sensation of open-air motoring paired with a powerful engine. Fuel economy considerations, while not entirely ignored, are secondary to the visceral experience.

City and highway performance

The EPA estimates for the M850i Convertible break down to 17 MPG in the city and 25 MPG on the highway. The city figure reflects the demands of stop-and-go traffic, where the V8’s displacement and the car’s overall weight are factors. Expect frequent trips to the gas station if you drive in urban areas. The highway figure, however, is more respectable. At a steady cruising speed, the eight-speed automatic transmission helps the engine settle into a more efficient rev range. Long road trips are certainly possible, though you’ll still be stopping for premium fuel more often than you would in a less performance-oriented vehicle.

Annual fuel cost

The EPA estimates the annual fuel cost for the 2020 BMW M850i xDrive Convertible at $2,900. This figure is based on driving 15,000 miles per year with a mix of city and highway driving, and assumes the use of premium gasoline. Remember that this is just an estimate; your actual fuel costs may vary depending on your driving habits, the local price of fuel, and how often you use the M850i’s available power. If you spend more time in the city or drive aggressively, expect to exceed that $2,900 mark. For those considering trading in a less powerful vehicle, this increase in fuel expenditure is part of the cost of owning the M850i.

Real-world expectations

While the EPA figures offer a baseline, real-world fuel economy often differs. Aggressive driving, particularly frequent full-throttle acceleration, impacts your MPG. But if you adopt a more relaxed driving style and prioritize smooth acceleration, you might nudge the numbers slightly higher. The M850i’s onboard computer provides real-time and average fuel consumption data, allowing drivers to monitor their efficiency. However, the temptation to exploit the V8’s performance is always there, and few M850i owners likely spend much time maximizing fuel economy.

How it compares

Compared to other high-performance convertibles, the M850i’s fuel economy is similar. A Mercedes-AMG SL63, for instance, achieves a similar 16 MPG city and 24 MPG highway, while a Porsche 911 Carrera Cabriolet averages around 20 MPG city and 27 MPG highway in rear-wheel drive form. The Jaguar F-Type R Convertible, with its supercharged V8, often comes in slightly lower in real-world figures. The Audi R8 Spyder, while offering supercar performance, suffers even more with its V10 engine. The M850I MPG across all years shows similar numbers, proving the engine and platform have found a sweet spot in delivering power. The comparison matters because buyers at this level have choices, and while fuel economy isn’t the most important factor, it’s still a consideration.

Tips to maximize efficiency

Use “Eco Pro” mode when possible. This setting remaps the throttle response and transmission shift points to prioritize fuel efficiency. It won’t turn the M850i into a Prius, but it can help you conserve fuel during long highway stretches or when commuting in light traffic.

Avoid unnecessary idling. Modern engines are designed to be shut off and restarted without significant wear, so if you’re stopped for more than a minute, consider turning off the engine. This is relevant in city driving, where idling at traffic lights can waste fuel.

Maintain proper tire inflation. Under-inflated tires increase rolling resistance, which hurts fuel economy. Check your tire pressures regularly and inflate them to the recommended levels, which can be found on the driver’s side doorjamb.

Anticipate traffic flow. Aggressive acceleration and hard braking waste fuel. By anticipating changes in traffic conditions and maintaining a smooth, consistent speed, you can improve your fuel economy and reduce wear on your car’s components.

Keep the car well-maintained. A properly tuned engine and clean air filter contribute to optimal fuel efficiency. Follow the recommended maintenance schedule and address any potential issues promptly to ensure your M850i is running well.

Ultimately, the M850i xDrive Convertible isn’t about squeezing every last mile out of a gallon of gasoline. It’s about the driving experience, and the fuel consumption is simply a consequence of that.