22 MPG combined is likely not the primary reason someone buys a 2018 Mercedes-Benz E400 Convertible. This is a car for sun-drenched weekend cruises, for making a statement about success, and for enjoying a refined driving experience. Fuel economy is a secondary consideration, but it’s something buyers should be aware of nonetheless. These are often second or third cars, toys for affluent owners rather than daily workhorses. So, while there are certainly more frugal choices out there, the E400 Convertible caters to a very specific desire, one where efficiency is less important than open-air luxury and effortless performance.

City and highway performance

The EPA estimates of 20 MPG in the city and 26 MPG on the highway reflect the realities of the E400 Convertible’s character. The city number reveals the trade-off for the potent 3.0L turbocharged V6 under the hood. Stop-and-go traffic will certainly take its toll.

On the open road, however, the nine-speed automatic transmission helps the E400 achieve a more reasonable highway figure, allowing the engine to cruise at lower RPMs when possible. But remember, the urge to exploit that readily available power will inevitably lead to lower real-world numbers, because no one buys a car like this to drive it like a Prius.

Annual fuel cost

According to the EPA, the annual fuel cost for the 2018 Mercedes-Benz E400 Convertible is estimated at $2,650. This calculation assumes 15,000 miles of driving per year, using the national average fuel price. Keep in mind that this is just an estimate, and your actual fuel costs will vary depending on your driving habits, the type of fuel you purchase, and where you live. Aggressive driving, frequent short trips, and premium fuel (which is recommended for optimal performance) will all increase this figure, so it’s worth factoring that into your budget.

Real-world expectations

While the EPA estimates provide a baseline, expect to see numbers slightly below the official figures in real-world driving. Drivers primarily using the E400 Convertible for leisurely weekend trips might come close to the highway estimate. However, those who use it more frequently in mixed driving conditions, or are prone to a heavy right foot, will likely see an average closer to 20 MPG.

Variables like weather, tire pressure, and vehicle maintenance also play a role in fuel efficiency. To explore E400 MPG across all years, you can continue your search here.

How it compares

The E400 Convertible occupies a rarefied space, but it still faces competition. The BMW 440i Convertible, for example, boasts similar performance with an EPA-estimated 25 MPG combined. The Audi S5 Cabriolet, with its sportier character, manages around 24 MPG combined. Even within the Mercedes-Benz family, the C-Class Cabriolet offers a slightly more efficient alternative. However, none quite match the E400’s presence and feeling of substantial luxury.

Buyers often compare the E400 against cars like the Lexus LC 500 Convertible, which is rated at just 18 MPG combined, making the German option seem economical. The decision depends on priorities: a slight increase in fuel economy versus the E400’s particular blend of comfort, style, and prestige. For more information you can view all Mercedes Benz fuel economy data.

Tips to maximize efficiency

While outright fuel economy isn’t the primary concern for E400 Convertible owners, there are still steps you can take to minimize fuel consumption.

Employ a gentle driving style whenever possible. The E400’s engine delivers plenty of power without needing to be constantly pushed to its limits. Smooth acceleration and anticipating traffic flow can make a noticeable difference.

Ensure your tires are properly inflated to the recommended pressure, which is usually found on a sticker inside the driver’s side doorjamb. Under-inflated tires increase rolling resistance, negatively impacting fuel economy.

Reduce unnecessary weight in the vehicle. Carrying extra cargo around adds to the engine’s workload, increasing fuel consumption. Remove any items you don’t need to have on board.

Take advantage of the E400’s ECO driving mode, if equipped. This mode optimizes various vehicle settings to prioritize fuel efficiency, such as altering throttle response and shift points.