The 2021 Mercedes-Benz GLS450 4matic achieves 21 MPG combined, an efficiency figure that most buyers of this model will anticipate. This isn’t a vehicle purchased for hypermiling; it’s a statement of success, wrapped in supple leather and boasting the three-pointed star. The GLS450 caters to those who prioritize space, luxury, and a commanding presence on the road, and its fuel economy is a secondary, though relevant, consideration.

City and highway performance

The EPA estimates of 20 MPG in the city and 24 MPG on the highway reflect the GLS450’s characteristics. The city figure highlights the engine’s effort to move over 5,300 pounds through stop-and-go traffic, and the toll of frequent acceleration. Out on the open road, the nine-speed automatic transmission allows the 3.0L inline-six engine to settle into a more efficient cruise, maximizing the benefit of its moderate hybrid assist system. These numbers are reasonable, given the vehicle’s size and capabilities, but owners will have to accept them.

Annual fuel cost

The EPA estimates the annual fuel cost for the 2021 Mercedes-Benz GLS450 4matic at $2,750. This calculation is based on driving 15,000 miles per year, with an assumed fuel price reflecting the national average. Actual fuel costs will vary depending on individual driving habits, local fuel prices, and the percentage of city versus highway driving. This $2,750 figure represents a benchmark for comparing the GLS450’s fuel consumption against other vehicles.

Real-world expectations

While the EPA provides a baseline, real-world MPG can vary. Aggressive driving, frequent short trips, and carrying heavy loads will all negatively impact fuel economy. Given the GLS450’s purpose as a family hauler and long-distance cruiser, expect to see numbers closer to or even slightly below the EPA estimates if you frequently travel with a full load of passengers and cargo. However, careful driving can potentially yield figures that match or even slightly exceed the EPA’s highway estimate of 24 MPG.

How it compares

The GLS450’s fuel economy places it in the middle of its competitors. The BMW X7 xDrive40i, with its similar inline-six engine, achieves a comparable 21 MPG combined. The Volvo XC90 T6 earns a slightly better 22 MPG combined, owing to its smaller, turbocharged and supercharged four-cylinder engine. Meanwhile, the Land Rover Range Rover Sport typically posts significantly lower MPG figures, sometimes falling below 18 MPG combined, especially when equipped with a supercharged V6 or V8. For buyers considering a plug-in hybrid option, the Volvo XC90 Recharge offers superior fuel economy in hybrid mode and the added benefit of all-electric driving for short distances. For those who are loyal to the brand, all Mercedes Benz fuel economy data can be found on this site. You can also view GLS450 MPG across all years to see how this model’s fuel economy has evolved over time.

Tips to maximize efficiency

Take it easy on the accelerator. The GLS450’s 362 horsepower provides ample power, but aggressive acceleration and hard braking will significantly reduce fuel economy. Treat the throttle with respect, especially in city driving, and allow the engine and transmission to work together smoothly.

Use the “Comfort” or “Eco” driving modes. These modes optimize the engine and transmission settings for better fuel efficiency. While the “Sport” mode offers a more engaging driving experience, it increases fuel consumption.

Maintain the correct tire pressure. Underinflated tires increase rolling resistance, which reduces fuel economy. Check your tire pressures regularly and ensure they are inflated to the recommended levels as specified on the driver’s side doorjamb.

Minimize aerodynamic drag. Remove any unnecessary roof racks or cargo carriers when not in use, as these create aerodynamic drag and reduce fuel efficiency. Also, avoid driving at high speeds for extended periods, as aerodynamic drag increases exponentially with speed.

Consider the weight you’re carrying. Hauling unnecessary cargo adds weight, which requires more energy to move. Regularly clear out any items you don’t need to optimize fuel economy, especially if you do not need the 7-passenger capacity of the GLS450.