22 MPG combined won’t top any efficiency charts, but for the 2018 Mercedes-Benz E400 4matic Convertible, it’s an acceptable trade-off. This car prioritizes open-air enjoyment with luxury and effortless power from its smooth turbocharged six-cylinder engine, not hypermiling. The target buyer seeks a refined driving experience and the Mercedes-Benz brand, and they’re willing to pay for it at the pump.

City and highway performance

The EPA estimates the E400 Convertible achieves 20 MPG in the city and 25 MPG on the highway. Stop-and-go driving, where the turbocharger spools up frequently and the nine-speed automatic transmission shifts gears, causes the city number. The highway figure is better, thanks to the transmission’s tall top gears that allow the engine to cruise at low RPMs. The convertible’s increased weight and aerodynamic drag, compared to the sedan, prevent it from matching the fuel economy of its closed-roof sibling. The 4matic all-wheel-drive system enhances grip and stability in all weather but adds weight, slightly reducing fuel efficiency compared to the rear-wheel-drive E400.

Annual fuel cost

The EPA estimates the annual fuel cost for the 2018 Mercedes-Benz E400 4matic Convertible at $2,650. This is based on driving 15,000 miles per year and using national average fuel prices. Your actual fuel cost will depend on your driving habits, location, and the price of premium gasoline, which this engine requires. Someone driving short city trips will likely exceed this estimate, while frequent highway trips might result in a lower annual cost.

Real-world expectations

Real-world fuel economy often differs from EPA figures. E400 Convertible drivers often report numbers close to the EPA’s estimates, but aggressive driving or frequent use of the car’s performance capabilities will lower the MPG. The turbocharged engine’s responsiveness is addictive, and using its power impacts fuel consumption. Consistent highway driving at legal speeds should yield results near or above the 25 MPG rating, while spirited city driving can easily drop the MPG into the high teens.

How it compares

The E400 Convertible competes with other luxury convertibles like the BMW 440i xDrive Convertible, which achieves a slightly better 25 MPG combined, reflecting BMW’s reputation for efficient engines. However, the Mercedes provides a different blend of luxury and comfort that some buyers prefer. The Audi A5 Cabriolet is another competitor, offering a combined MPG of 27 with its smaller turbocharged four-cylinder, but sacrificing some of the E400’s power and prestige. The Lexus LC 500 Convertible has a powerful V8 engine but significantly lower fuel economy of 18 MPG combined. These comparisons highlight the E400’s position as a middle-ground option, balancing performance, luxury, and efficiency. You can find all all Mercedes Benz fuel economy data here, including E400 MPG across all years.

Tips to maximize efficiency

Use the E400’s driving modes. “Eco” mode softens throttle response, optimizes shift points, and reduces climate control load to improve fuel economy. It might slightly diminish the car’s sporty feel, but makes a noticeable difference on longer trips or in traffic.

Gentle acceleration is key to maximizing efficiency in any turbocharged vehicle. Avoid aggressive throttle that forces the turbocharger to work harder, which consumes more fuel. Smooth acceleration allows the engine to operate efficiently.

Maintain proper tire inflation. Underinflated tires increase rolling resistance, reducing fuel economy. Check your tire pressures and inflate them to the levels on the doorjamb. This simple step can affect fuel efficiency.

Minimize weight. Remove items from the trunk and interior to reduce the vehicle’s weight. Extra weight increases fuel consumption, especially during acceleration and climbing hills.

Plan your trips. Combine errands and avoid unnecessary trips to minimize driving distance and fuel consumption. A little planning can save time and money at the pump.