26 MPG combined in the 2015 Mercedes-Benz SLK250 isn’t going to set any efficiency records, but it’s a reasonable compromise between open-top thrills and running costs. No one buys this roadster expecting Prius-level fuel economy. They buy it for the image, the retractable hardtop, and the engaging driving experience that Mercedes-Benz delivers; fuel economy is a secondary consideration in this segment, but one that must still remain within acceptable limits.

City and highway performance

The SLK250’s EPA estimates are 23 MPG in the city and 32 MPG on the highway. The city figure reflects the realities of stop-and-go driving and the engine working harder at lower speeds and during frequent acceleration. The highway number, on the other hand, demonstrates the efficiency gains achieved at a steady cruise. The 7-speed automatic transmission plays an important role here, keeping the engine in its optimal rev range for fuel efficiency when you’re driving long distances.

Annual fuel cost

The EPA estimates that the annual fuel cost for the 2015 Mercedes-Benz SLK250 will be $2,250. This figure is based on driving 15,000 miles per year and using national average fuel prices. Your actual fuel costs may vary depending on how much you drive, your driving habits, and the price of gasoline in your area, but the EPA number offers a standardized baseline for comparison.

Real-world expectations

The EPA numbers offer a good starting point, but expect some variance in the real world. Enthusiastic driving, with frequent use of the turbocharger’s boost, will reduce your MPG. Consistently smooth driving and prioritizing early upshifts will help you approach the EPA numbers. Keep in mind that factors like tire pressure, ambient temperature, and even the type of gasoline you use can have an impact on your fuel economy.

How it compares

Compared to other roadsters of its era, the SLK250’s fuel economy holds up pretty well. The BMW Z4 sDrive28i, with its 2.0L turbocharged engine, also achieves around 26 MPG combined. The Audi TT Roadster, equipped with its 2.0L turbo four, offers similar figures. The Porsche Boxster, while offering a more focused driving experience, doesn’t quite match the SLK250’s efficiency, landing closer to 24 MPG combined in its base configuration. These slight variations in MPG can be a factor for the budget-minded roadster enthusiasts, though typically less important that the actual driver experience for this buyer.

Tips to maximize efficiency

Use the SLK250’s Eco mode, this setting adjusts the throttle response and transmission mapping to prioritize fuel efficiency. Consider this mode in city driving and highway cruising. It might feel less sporty than the standard setting, but it can yield a noticeable improvement in MPG over the long run, particularly if you tend to accelerate quickly.

Ensure your tires are properly inflated to the recommended pressure. Low tire pressure increases rolling resistance, forcing the engine to work harder and consume more fuel. Check your tire pressure regularly, especially during temperature changes; proper inflation helps both with fuel economy and tire wear.

Avoid excessive idling. Today’s engines warm up quickly, so there’s no need to let the car idle for an extended period, particularly in warm weather. If you’re waiting for someone or stopped for more than a minute, turn off the engine. Restarting the car consumes less fuel than idling for extended periods.

Remember that the roof impacts aerodynamics! Driving with the top down will reduce MPG slightly, especially at higher speeds. Raising the roof on long highway trips or when driving in strong head winds can improve fuel efficiency and reduce cabin noise.

Keep up with your SLK250’s scheduled maintenance. Regular oil changes, air filter replacements, and spark plug maintenance will ensure that the engine is running at peak efficiency. A neglected engine will burn more fuel and produce less power. View all Mercedes Benz fuel economy data in our data set, or narrow the view to SLK250 MPG across all years.