The 2015 Mercedes-Benz E400 Convertible gets 23 MPG combined, which is reasonable. It offers strong performance from a refined turbocharged six-cylinder engine and a beautifully appointed interior for open-air motoring. This car is a statement of success. Fuel economy is a consideration, balanced against the desire for comfort, luxury, and the prestige a Mercedes-Benz convertible provides. Buyers who want the best fuel economy are not looking at this type of car. They probably want a small diesel sedan. See all Mercedes Benz fuel economy data.

City and highway performance

EPA estimates for the E400 Convertible are 20 MPG in the city and 29 MPG on the highway. The city mileage reflects the car’s weight and city driving. Stop-and-go traffic hurts fuel efficiency. The highway number is better because the 7-speed automatic transmission allows the engine to cruise at relatively low RPMs, helping highway fuel economy. The 3.0L V6 is turbocharged but isn’t overly stressed when cruising, which helps efficiency on long journeys. This fits with the E400 Convertible’s purpose: weekend trips and road trips.

Annual fuel cost

The EPA estimates the annual fuel cost for the 2015 Mercedes-Benz E400 Convertible at $2,500. This is based on driving 15,000 miles per year, with 45% in the city and 55% on the highway, using national average fuel prices. This is a benchmark, but individual costs will vary based on driving habits and local fuel prices. Someone who drives the E400 mainly for short city trips will likely exceed $2,500, while someone who mainly drives on the highway might spend less. Keep in mind that this is a premium vehicle that requires premium fuel, raising the overall cost.

Real-world expectations

EPA estimates are a baseline, but real-world fuel economy differs. Aggressive driving, air conditioning, and tire pressure affect MPG. Owner reports show that achieving the EPA’s 29 MPG highway rating is possible, especially on longer trips. The 20 MPG city figure can be harder to reach, especially in congested areas. Most owners will probably see a combined MPG closer to 21 or 22 MPG. You can see E400 MPG across all years for a sense of variations.

How it compares

The 2015 BMW 435i Convertible gets similar city and highway figures (around 22 MPG combined), though some models may offer slightly better economy due to engine tuning. The Audi A5 Cabriolet, with its smaller turbocharged four-cylinder engine, typically offers a few MPG better, around 25 MPG combined, but it can lack the V6’s power. These differences might not matter to the buyer who wants the Mercedes-Benz name, its interior, and its blend of comfort and performance, and who might see it as worth the reduced fuel efficiency compared to some competitors.

Tips to maximize efficiency

Smooth acceleration is key. The E400’s turbocharged engine provides torque, so there’s no need to aggressively accelerate. Gradual starts save fuel and match the car’s luxury character.

Keep proper tire pressure. Underinflated tires increase rolling resistance, which reduces fuel economy. Check your tire pressure and inflate them to the levels listed on the sticker inside the driver’s side doorjamb.

Avoid idling. Idling wastes fuel. If you’re stopped for over a minute, especially in traffic, turn off the engine. The E400 lacks a stop/start system, so manually shutting off the engine helps over time.

Watch your speed on the highway. Aerodynamic drag rises quickly with speed, so driving at a constant, moderate speed (around 65-70 mph) will improve fuel economy compared to higher speeds. Use cruise control to keep a steady pace.