23 MPG combined is an acceptable fuel economy figure for the 2016 Mercedes-Benz SL400. This isn’t a vehicle purchased for the sake of efficiency. Buyers prioritize open-top driving pleasure, the prestige of the Mercedes-Benz brand, and the confident performance of its turbocharged six-cylinder engine. Fuel economy is secondary, a necessary compromise for the driving experience this roadster delivers.

City and highway performance

The EPA estimates the SL400 at 20 MPG in the city and 27 MPG on the highway. The city figure reflects the stop-and-go driving conditions where the engine is frequently idling or accelerating, conditions not ideal for maximizing fuel efficiency. The highway figure showcases the potential of the 3.0L engine when cruising at steady speeds. The 7-speed automatic transmission also plays a role, selecting optimal gears to keep the engine in its most efficient operating range on the open road. However, aggressive acceleration, a common temptation in a car like this, will quickly decrease observed mileage compared to these figures.

Annual fuel cost

The EPA estimates the annual fuel cost for the 2016 Mercedes-Benz SL400 at $2,500. This figure is based on driving 15,000 miles per year and using the EPA’s projected fuel prices. This is an estimate, your actual fuel costs will vary depending on your driving habits, the type of fuel you use (premium is recommended for the SL400), and of course, fluctuations in fuel prices. Drivers who primarily travel short distances in the city, relish frequent bursts of acceleration, or live in areas with higher fuel costs will likely exceed this $2,500 projection.

Real-world expectations

While the EPA figures provide a baseline, real-world fuel economy for the SL400 will vary. Expect to see numbers slightly below 23 MPG combined if you frequently drive aggressively or spend most of your time in the city. Owners who prioritize fuel efficiency and spend considerable time on the highway at consistent speeds may achieve numbers closer to the EPA’s 27 MPG highway estimate. The car’s driving mode also influences consumption. Selecting “Eco” mode prioritizes fuel efficiency by optimizing throttle response and shift points. “Sport” and “Sport+” modes, on the other hand, prioritize performance and will use more fuel. See SL400 MPG across all years.

How it compares

Compared to other luxury roadsters, the fuel economy of the SL400 is competitive. The BMW Z4 sDrive35i, with its 3.0L inline-six, achieves around 20 MPG combined. The Porsche 718 Boxster S, known for its performance, delivers around 22 MPG combined. What’s critical to understand is that these vehicles represent a very small and specific segment of the market. Buyers of these automobiles prioritize driving experience and prestige over ultimate fuel efficiency. The SL400 offers a more balanced combination of luxury and performance than some of its sportier competitors, which influences who finds this MPG acceptable.

Tips to maximize efficiency

Ensure your tires are properly inflated. Underinflated tires increase rolling resistance, forcing the engine to work harder and consume more fuel. Regularly check your tire pressure and inflate them to the recommended levels specified on the doorjamb sticker. This simple step can improve fuel economy noticeably.

Avoid aggressive driving. Rapid acceleration and hard braking significantly decrease fuel economy. Smooth and gradual acceleration, combined with anticipating traffic conditions, will help you conserve fuel. The SL400’s ample power is tempting but restrain yourself to maximize efficiency.

Use cruise control on the highway. Maintaining a consistent speed on the highway helps optimize fuel efficiency. Cruise control minimizes unnecessary acceleration and deceleration, keeping the engine in its most efficient operating range. Even in this class of vehicle, consistency and control are useful.

Keep up with routine maintenance. Regular oil changes, air filter replacements, and spark plug maintenance are all important for optimal engine performance and fuel efficiency. A well-maintained engine operates more efficiently, consuming less fuel. Consult your owner’s manual for the recommended maintenance schedule. Consider looking at all Mercedes Benz fuel economy data alongside maintenance schedules.

Minimize idling. Excessive idling wastes fuel. If you anticipate being stopped for more than a minute, turn off the engine. Restarting the engine consumes less fuel than idling for an extended period. This is even more important in older engines where fuel injection and catalytic converters may not be as efficient as more modern designs.