The 2018 Mercedes-Benz GLS450 4MATIC gets an EPA-estimated 19 MPG combined. It’s not the most fuel-efficient SUV, but buyers accept this trade-off for a large, luxurious, and capable family vehicle with the Mercedes-Benz brand. These buyers prioritize space, comfort and the prestige the GLS450 offers over fuel efficiency.

City and highway performance

The 2018 GLS450’s EPA ratings are 17 MPG in the city and 22 MPG on the highway. The city figure reflects the impact of stop-and-go traffic on the large SUV’s weight and efficiency. On the open road, the 9-speed automatic transmission allows the turbocharged 3.0-liter V6 to run at lower RPMs, which helps achieve the better highway number. However, aggressive driving and high speeds will reduce that figure.

Annual fuel cost

The EPA estimates the annual fuel cost for the 2018 Mercedes-Benz GLS450 4MATIC at $3,050. This is based on driving 15,000 miles per year, with a specific percentage for city and highway driving, using national average fuel prices. If you drive more than 15,000 miles annually, or if fuel prices are higher in your area, your actual costs will be higher. This number provides a baseline, but driving habits greatly affect fuel costs.

Real-world expectations

The EPA provides standardized testing, but real-world MPG can vary. Driving style (aggressive acceleration and braking), traffic, terrain, and tire pressure can all change fuel consumption. Drivers who often tow or carry heavy loads in their GLS450 should expect lower fuel economy than those who use it for commuting or family trips. Routine maintenance is also important. A neglected engine or underinflated tires can hurt efficiency. To learn about GLS450 MPG across all years, comparing model years might show differences or insights based on user-reported data.

How it compares

The GLS450’s fuel economy is similar to other SUVs, but not the best. For example, the Acura MDX with all-wheel drive gets 21 MPG combined, which is slightly better, but it isn’t as large or luxurious as the GLS450. The BMW X5 xDrive40i, with a similar turbocharged inline-six, gets around 22 MPG combined and is a closer competitor. Land Rover’s Range Rover Sport offers similar luxury and off-road capability, but typically gets around 19 MPG combined with its supercharged V6. These comparisons are important for GLS450 buyers who are looking at the total cost of ownership, balancing fuel costs with size, luxury, and brand.

Be sure to explore all Mercedes Benz fuel economy data when making your decision.

Tips to maximize efficiency

Use the GLS450’s drive mode selector. “Eco” mode optimizes the engine and transmission for efficiency, resulting in smoother acceleration and earlier upshifts. It’s not ideal for fast driving, but it can help on longer drives.

Check your tire pressure often. Underinflated tires increase rolling resistance, making the engine work harder and use more fuel. See the sticker on the driver’s side doorjamb for the correct tire pressure and keep your tires properly inflated.

Avoid idling. If you’ll be stopped for more than a minute, turn off the engine. Modern engines restart quickly, and idling wastes fuel.

Reduce aerodynamic drag by removing roof racks or cargo carriers when not in use. These add wind resistance, especially at high speeds. Keeping the windows closed on the highway can also help.