23 MPG combined isn’t going to win any hypermiling competitions, but for the 2015 Mercedes-Benz SL400, it’s an acceptable trade-off for the refined performance and open-air experience this roadster provides. This isn’t a car primarily bought for its fuel economy. Instead, it’s purchased by those seeking a blend of luxury, performance, and iconic styling, where fuel efficiency plays a secondary, but relevant, role.

City and highway performance

The SL400’s individual EPA ratings of 20 MPG in the city and 27 MPG on the highway highlight its suitability for both relaxed cruising and spirited driving. The city figure reflects the stop-and-go conditions where the 3.0L turbocharged V6 works harder, while the 27 MPG highway rating demonstrates its ability to deliver respectable efficiency on longer journeys. Owners who primarily use their SL400 for weekend getaways or scenic drives will likely see numbers closer to that highway figure, while those navigating dense urban environments can expect to be closer to 20 MPG.

Annual fuel cost

According to EPA estimates, the annual fuel cost for the 2015 Mercedes-Benz SL400 is $2,500. This figure is based on driving 15,000 miles per year and using national average fuel prices. Note that fluctuations in gasoline prices and your individual driving habits can significantly impact this number. Owners who drive fewer miles or carefully manage their driving style may see a lower annual fuel expenditure, while those with a heavier foot or longer commutes might find themselves exceeding this estimate.

Real-world expectations

While EPA ratings provide a standardized benchmark, real-world fuel economy can vary substantially. Factors like driving style, terrain, and even tire pressure can all influence MPG. SL400 owners who prioritize spirited acceleration and frequently engage the car’s Sport or Manual shifting modes should anticipate somewhat lower fuel economy than the EPA estimates. Conversely, those who adopt a more relaxed driving style and use the car’s Eco mode can potentially exceed the official ratings, especially on long highway drives.

Monitoring your car’s trip computer and adjusting your driving habits accordingly can help you get the most out of each gallon. Even meticulous maintenance, like keeping tires properly inflated, can improve overall miles per gallon.

How it compares

In the realm of luxury roadsters, the SL400’s fuel economy lands somewhere in the middle. The BMW Z4 sDrive35i, with its 3.0L inline-6, offers similar performance and fuel economy, hovering around 26 MPG combined, depending on the specific configuration. A Porsche 718 Boxster, known for its sharper handling, can achieve around 24 MPG combined, placing it very close to the SL400. Comparing the SL400 to a Jaguar F-Type convertible reveals that the Jaguar, particularly with its supercharged V6 or V8 engines, typically consumes more fuel.

For potential buyers considering all Mercedes Benz fuel economy data, it’s important to remember they want a luxurious driving experience, even if that means less gas at the pump. Understanding these trade-offs and considering your individual priorities is critical when choosing between these alternatives. Also consider the full history of SL400 MPG across all years to see how fuel economy varied over time.

Tips to maximize efficiency

Use the SL400’s Eco mode. This setting optimizes the engine and transmission for maximum efficiency, resulting in a noticeable improvement, especially during city driving. Eco mode softens throttle response, encouraging a smoother driving style that minimizes fuel consumption.

Pay attention to your tire pressure. Maintaining the correct tire pressure, as indicated on the doorjamb sticker, can reduce rolling resistance and improve fuel economy. Check your tire pressures regularly, ideally once a week, and adjust as needed.

Avoid excessive idling. Letting your engine idle for extended periods, especially in traffic, wastes fuel. If you anticipate being stopped for more than a minute, consider turning off the engine. Modern engines are designed to restart quickly and efficiently.

Schedule regular maintenance. Keeping your SL400 properly maintained, including regular oil changes, air filter replacements, and spark plug inspections, ensures that the engine is running at peak efficiency. A well-maintained engine consumes less fuel and produces fewer emissions.

Anticipate traffic flow. By looking ahead and anticipating traffic patterns, you can avoid unnecessary acceleration and braking, which can significantly impact fuel economy. Maintaining a steady speed and avoiding sudden changes in throttle position will help you maximize MPG.