24 MPG combined isn’t the main reason someone chooses a 2018 BMW M240i Convertible, and BMW and its customers are aware of this. It’s not a Prius, it’s a compact, rear-wheel-drive (or optional xDrive all-wheel-drive) convertible designed for spirited driving first, with fuel efficiency a distant second. This number reflects the combination of a potent 3.0L turbocharged inline-six engine with an eight-speed automatic transmission in a car that invites enthusiastic driving. Buyers prioritize the thrill of open-top motoring and the iconic BMW driving experience over fuel-saving techniques.

City and highway performance

The M240i Convertible achieves its EPA ratings through a mix of city and highway driving. The 21 MPG city figure shows the fuel cost of stop-and-go traffic, where the engine’s responsiveness and the automatic transmission’s eagerness to downshift lead to more fuel consumption. However, the 30 MPG highway rating shows the engine’s efficiency at cruising speeds. The tall gears of the eight-speed transmission allow the engine to run at lower RPMs, reducing fuel use on long trips when the top is up, which improves the aerodynamics.

Annual fuel cost

The EPA estimates the annual fuel cost for the 2018 BMW M240i Convertible at $2,400. This figure is based on driving 15,000 miles per year, with 45% of those miles driven in the city and 55% on the highway. The calculation uses the national average fuel price when the EPA data was compiled. Fuel costs will vary depending on local gas prices and driving habits, but the $2,400 figure provides a useful benchmark. This also doesn’t factor in the premium fuel requirement, a common trait among performance cars like this. Budget accordingly.

Real-world expectations

The EPA ratings provide a standardized comparison, but real-world fuel economy for the M240i Convertible will vary. Drivers who frequently use the engine’s power and enjoy aggressive acceleration will likely see figures closer to the city rating. On the other hand, those who drive conservatively and prioritize smooth, consistent driving can potentially achieve numbers closer to or even slightly above the highway rating. Driving conditions also play a role. Heavy traffic, hilly terrain, and extreme temperatures can all negatively impact fuel economy. Consider exploring M240I MPG across all years.

How it compares

Compared to its competitors, the M240i Convertible’s fuel economy is competitive, but not the best in its class. For example, the Audi S3 Sedan, with its 2.0L turbocharged four-cylinder, achieves a combined 25 MPG. A Mercedes-Benz C300 Cabriolet, featuring a 2.0L turbo four, manages a similar 25 MPG combined rating. These differences are not drastic, but they show the trade-off between the M240i’s inline-six power and fuel consumption. The Porsche 718 Boxster, though a mid-engine roadster, offers a similar level of performance but often with slightly lower MPG. These comparisons matter because the M240i buyer, while not solely focused on efficiency, is still aware of alternatives and wants to understand the relative cost of performance. For further comparison, view all Bmw fuel economy data.

Tips to maximize efficiency

The M240i Convertible isn’t primarily designed for fuel efficiency, but several techniques can help improve MPG. Avoid aggressive acceleration and hard braking. The engine’s responsiveness can be tempting, but smooth, gradual acceleration will conserve fuel. Anticipate traffic flow and maintain a consistent speed whenever possible. Using cruise control on the highway will help to avoid unnecessary speed fluctuations.

Make sure that your tires are properly inflated. Underinflated tires increase rolling resistance, which reduces fuel economy. Check your tire pressure regularly and inflate them to the manufacturer’s recommended levels. The recommendation can usually be found on a sticker inside the driver’s side door jamb.

Minimize idling. Avoid letting the engine idle for extended periods, especially in cold weather. Modern engines warm up quickly when driving, and idling only wastes fuel. If you’re stopped for more than a minute, it’s generally more efficient to turn off the engine.

Use the “Eco Pro” driving mode, if equipped. Eco Pro mode alters the engine mapping, transmission shift points, and climate control settings to prioritize fuel economy. The trade-off is reduced performance, but it can be useful in situations where improving MPG is desired.

Reduce aerodynamic drag. The convertible top is often lowered for enjoyment, but keeping it raised at higher speeds can improve fuel economy by reducing drag. Also, remove any unnecessary cargo from the vehicle, as excess weight also impacts fuel efficiency.