24 MPG combined is not the main reason someone buys a 2024 BMW 840i xDrive Convertible. This isn’t a Prius for top-down thrills, it’s a meticulously crafted machine designed to deliver an experience, not just transport you from A to B. The 840i Convertible attracts a buyer who prioritizes luxurious open-air motoring, strong performance, and head-turning style above all else. Fuel economy is a consideration, but rarely the deciding factor.

City and highway performance

The EPA estimates 21 MPG in the city and 29 MPG on the highway. The city figure reflects the stop-and-go nature of urban driving; the 840i’s turbocharged 3.0L inline-six, while efficient for its output, still requires fuel to repeatedly accelerate its weight. The highway figure is more appealing. The 8-speed automatic transmission works to keep the engine in its most efficient range at cruising speeds, and the turbocharged engine requires less effort to maintain momentum on open roads. Those who frequently take long road trips will find the highway MPG more representative of their typical fuel consumption.

Annual fuel cost

The EPA estimates the annual fuel cost for the 2024 BMW 840i xDrive Convertible at $2,400. This figure is based on driving 15,000 miles per year, with 55% of those miles driven in the city and 45% on the highway. The calculation uses the national average fuel price, which fluctuates, meaning your actual fuel costs may be higher or lower depending on where you live and how you drive. For example, those who do most of their driving in premium-fuel-heavy California should expect a considerably higher figure, while those in states with lower gas taxes will see some savings.

Real-world expectations

The EPA estimates are a useful benchmark, but real-world fuel economy will vary based on driving habits, environmental conditions, and vehicle maintenance. Spirited driving, with frequent use of the turbocharged engine’s ample power, will certainly reduce fuel efficiency. Conversely, gentle acceleration, consistent speeds, and regular maintenance can help you achieve figures closer to the EPA estimates. Also, understand that the xDrive all-wheel-drive system, while enhancing traction and stability, slightly increases drag and therefore impacts fuel economy compared to a rear-wheel-drive variant if one were available.

How it compares

Compared to its key competitors, the 840i xDrive Convertible occupies a predictable position. The Mercedes-Benz SL 55 AMG, for example, delivers a significantly lower 16 MPG combined due to its higher-performance engine and standard all-wheel drive. The Porsche 911 Carrera Cabriolet, depending on configuration, can achieve slightly better fuel economy, with some models reaching around 20 MPG combined. Comparing all Bmw fuel economy data reveals that the 840i Convertible is one of the least fuel-efficient models in the lineup. This comparison matters because the 840i Convertible buyer is cross-shopping prestigious brands and weighing performance against relative efficiency within this exclusive segment. You can also view the 840I MPG across all years.

Tips to maximize efficiency

Maintain consistent speeds and avoid sudden acceleration and braking. The 840i Convertible, while capable of acceleration, consumes less fuel when driven smoothly. Anticipate traffic flow and use engine braking when possible to minimize the need for hard braking. This simple change in driving style will save you money.

Ensure proper tire inflation. Underinflated tires increase rolling resistance, forcing the engine to work harder and burn more fuel. Check your tires regularly and inflate them to the pressure recommended on the doorjamb sticker. This is especially critical for a heavy vehicle like the 840i Convertible.

Minimize unnecessary weight. Carrying extra weight in the trunk or passenger compartment reduces fuel economy. Remove any unnecessary items to lighten the load and improve efficiency. This advice applies to all vehicles, but is particularly relevant to a vehicle whose performance is often enjoyed.

Consider using the Comfort or Eco Pro driving modes when less gas is important. These modes adjust the engine and transmission settings to optimize fuel consumption. While you may sacrifice some of the 840i Convertible’s sporty responsiveness, the fuel savings can be significant, especially on longer trips. Save the Sport and Sport+ modes for when you want to exploit the engine’s full potential.