29 MPG combined isn’t the number one reason why someone buys the M340i, but it’s a figure they can live with given the performance. This is a sport sedan that delivers a driving experience that’s engaging and rewarding. Fuel economy, while important, plays a supporting role. This car is for enthusiasts who appreciate a responsive engine, sharp handling, and a comfortable ride, not hypermilers obsessed with squeezing every last drop of fuel.

City and highway performance

The EPA estimates the M340i will achieve 27 MPG in the city and 33 MPG on the highway. These figures show the engine’s efficiency, its 8-speed automatic transmission, and BMW’s attention to detail in optimizing aerodynamics and weight. City driving, with its stop-and-go nature, typically takes the biggest toll on fuel economy, but the M340i manages to mitigate this effect thanks to its drivetrain’s ability to quickly respond to throttle inputs and efficiently manage power delivery. On the highway, the engine settles into a relaxed cruise, further improving efficiency. The overdriven eighth gear allows the engine to operate at lower RPMs, reducing fuel consumption without sacrificing responsiveness when needed.

Annual fuel cost

According to EPA estimates, the annual fuel cost for the M340i is $2,000. This figure is based on driving 15,000 miles per year and using national average fuel prices. Individual results will vary depending on driving habits, local fuel prices, and other factors. Someone who lives in an area with high gas prices or drives aggressively is likely to exceed this estimate, while someone who drives primarily on the highway and practices fuel-efficient driving techniques may spend less. The $2,000 figure provides a baseline for understanding the M340i’s running costs, placing it within a range that’s acceptable for many luxury car buyers. You can compare this figure to all Bmw fuel economy data to see how similar models rate.

Real-world expectations

While the EPA provides a standardized benchmark, real-world fuel economy often differs. M340I MPG across all years shows a range of real-world data reported by drivers. Expect to see figures in the low 20s during enthusiast driving, especially with frequent use of Sport or Sport+ drive modes. If most of your driving is on local highways and you don’t accelerate too hard, expect figures in the mid to upper 30s. The onboard computer provides a good indication of recent fuel consumption, but keep in mind that short trips with a cold engine will always negatively impact your mileage.

How it compares

The M340i competes with other performance sedans. The Audi S4, for example, achieves around 24 MPG combined, making the M340i a more efficient choice. The Mercedes-AMG C43 comes in around 21 MPG. These differences, while relatively small on a percentage basis, can add up over the course of ownership. Buyers who prioritize less gas might also consider the Lexus IS 350, which returns around 23 MPG, though it lacks the M340i’s performance. The Acura TLX Type S also gets around 21 MPG. People who are looking at the M340i aren’t likely choosing a competitor because of only a small difference in MPG, but instead they are buying for the engine, looks, or driving experience. The M340i balances performance and fuel efficiency.

Tips to maximize efficiency

Use the M340i’s Eco Pro driving mode. This mode recalibrates the throttle response and transmission mapping to prioritize fuel efficiency, resulting in smoother acceleration and earlier upshifts. While it may reduce the car’s responsiveness, it can significantly improve fuel economy during everyday driving, and you can switch the driving mode as needed.

Avoid aggressive acceleration and braking. The M340i’s powerful engine is tempting to use to its fullest potential, but doing so burns fuel quickly. Gentle acceleration and smooth braking help maintain momentum and reduce fuel consumption. Anticipating traffic conditions and avoiding unnecessary stops can also make a difference.

Maintain proper tire inflation. Underinflated tires increase rolling resistance, which reduces fuel economy. Check your tire pressure regularly and inflate them to the recommended levels, which are typically found on a sticker inside the driver’s side doorjamb or in the owner’s manual.

Minimize idling time. Idling consumes fuel without covering any distance. If you anticipate being stationary for more than a minute or two, it’s best to turn off the engine. The M340i’s automatic start-stop system helps, automatically shutting off the engine at stoplights and other brief pauses. If you find the system intrusive, you can disable it, but keep in mind that doing so will reduce fuel efficiency.