The 2019 Mercedes-Benz SL450 gets 23 MPG combined. It’s not a fuel-sipping champion, but it’s not a gas guzzler either. The SL450 is a luxury roadster, designed for open-top cruising and effortless performance. Fuel economy is a consideration, but it’s further down the list for buyers. They prioritize the thrill of the twin-turbo V6, the sumptuous leather interior, and the Mercedes-Benz brand. They understand that performance and luxury cost money, and they’re willing to pay.

City and highway fuel economy

The EPA estimates 20 MPG in the city and 28 MPG on the highway. This split reflects how the SL450 drives. In urban environments, stop-and-go traffic lowers fuel consumption. The 3.0L V6, while responsive, isn’t efficient in these conditions. However, on the open road, the nine-speed automatic transmission allows the engine to cruise at lower RPMs, for better highway mileage. The SL450 is most at home on long stretches of winding coastal roads, where its performance and efficiency can be best enjoyed.

Annual fuel cost

The EPA calculates an annual fuel cost of $2,500 for the 2019 Mercedes-Benz SL450. This is based on driving 15,000 miles per year, current national average fuel prices, and the car’s combined MPG rating. This is just an estimate, as individual driving habits, local fuel prices, and the type of fuel used can all change the actual cost. Drivers who spend more time in the city or accelerate more will likely exceed this estimate, while those who primarily cruise on the highway might find it a bit high. It’s a useful benchmark, but personal experience may vary.

Real-world expectations

The EPA provides a standardized rating, but real-world MPG can differ. SL450 owners report figures close to the official estimates, but lifestyle matters. Weekend joyrides with the top down won’t match the EPA’s ideal scenario. Hard acceleration to hear the exhaust will lower fuel economy. However, for owners who drive more conservatively, achieving or exceeding the 28 MPG highway figure is possible. Consider visiting SL450 MPG across all years to compare ratings.

How it compares

The SL450 is unique, and its fuel economy should be viewed in that context. The BMW Z4 M40i, for example, achieves an EPA-estimated 25 MPG combined, offering slightly better efficiency. The Porsche 718 Boxster gets around 24 MPG depending on the engine and options. Refer to all Mercedes Benz fuel economy data for more information. While these alternatives might offer marginal fuel savings, buyers often choose the SL450 for its luxury, prestige, and styling. The Jaguar F-Type is another competitor within the sports car class, delivering around 23 MPG combined on its base model, but efficiency decreases with higher performance engines. The small MPG difference often becomes less important than brand preference, design, and how the car drives. Small fuel economy differences are rarely a deciding factor in this segment.

Tips to maximize efficiency

Avoid accelerating hard. The SL450’s twin-turbo V6 is eager to respond, but each burst of power uses more fuel. Smooth acceleration will improve fuel economy while still being enjoyable. Let the engine’s torque do the work, instead of relying on high RPMs.

Keep your tires properly inflated. Underinflated tires increase rolling resistance, using more fuel. Check your tire pressure regularly, and use the recommended pressures listed on the doorjamb sticker. Also, make sure your tires are aligned, as misalignment can cause uneven wear and increased rolling resistance.

Minimize idling. Letting the engine idle for a long time wastes gas. If you’re stopped for more than a minute, turn off the engine. The SL450’s engine restarts quickly, making this an easy way to save fuel, especially in urban traffic.

Use cruise control on the highway. Maintaining a consistent speed helps fuel economy. Cruise control minimizes unnecessary acceleration and deceleration, improving efficiency. Watch for terrain changes and adjust speed accordingly.

Think about using a lighter weight synthetic oil. While Mercedes specifies a particular oil weight, asking a trusted mechanic about a slightly lighter synthetic oil could slightly improve fuel economy. The lower viscosity can reduce internal engine friction. Only consider this with expert advice to protect the engine.