16 MPG combined isn’t going to win any green awards, but for the 2017 Mercedes-Benz GLS550 4Matic, it’s almost beside the point. This isn’t a vehicle purchased by buyers prioritizing lower fuel costs. This is a seven-passenger luxury SUV, built for comfortably hauling families and their gear in opulent surroundings, powered by a muscular V8 engine designed to deliver effortless thrust. The 16 MPG is simply the price of admission.

City and highway performance

The EPA estimates of 14 MPG in the city and 18 MPG on the highway reflect the realities of moving a vehicle of this size and weight. Urban driving involves frequent stop-and-go traffic, using the 4.7-liter V8’s abundant torque, thus impacting fuel consumption. The nine-speed automatic transmission tries valiantly to keep the revs down, but the engine’s inherent thirst is undeniable. On the open road, the GLS550 fares slightly better, but its aerodynamic profile and substantial weight still limit its efficiency. Highway MPG may be achieved on long, mostly flat highway stretches, but is easily diminished by hills or higher speeds.

Annual fuel cost

The EPA estimates the annual fuel cost for the 2017 Mercedes-Benz GLS550 4Matic at $3,600. This figure is based on driving 15,000 miles per year, with 55% of those miles driven in the city and 45% on the highway. It also assumes a national average fuel price. For GLS550 owners, who likely live in areas with higher-than-average fuel costs, and who value premium fuel, this number could easily be higher. For many who choose this vehicle, this expense is factored into the overall cost of ownership alongside insurance, maintenance, and the initial purchase price. While the GLS550 is expensive to fuel, its drivers prioritize its luxury, performance, and practicality over pure fuel savings.

Real-world expectations

While the EPA provides a standardized estimate, real-world fuel economy can vary widely based on individual driving habits, traffic conditions, and even weather. Aggressive acceleration, frequent short trips, and driving in mountainous terrain will all negatively impact fuel consumption. Conversely, gentle acceleration, consistent highway speeds, and proper vehicle maintenance can help maximize efficiency. It’s likely that most GLS550 owners will see numbers that fluctuate around the EPA estimates, albeit closer to the lower end of the range under most normal circumstances.

How it compares

Compared to other SUVs in its class at the time, the 2017 GLS550’s fuel economy was generally in line with other V8-powered offerings. The BMW X5 xDrive50i, with its 4.4-liter V8, achieved similar figures. The Cadillac Escalade, with its larger 6.2-liter V8, offered slightly worse MPG, around 17 MPG combined. Even stepping down to a smaller six-cylinder engine, like the Volvo XC90 T6, only netted around 22 MPG combined, a far cry from the GLS550. This comparison matters because the GLS550 buyer often isn’t cross-shopping with dramatically more efficient vehicles. They’re comparing its performance and features against similar luxury SUVs, accepting the fuel cost as part of the ownership experience. See all Mercedes Benz fuel economy data to compare. And for a deeper dive into specific model years, consult GLS550 MPG across all years.

Tips to maximize efficiency

This first tip is simple, yet critical: use cruise control whenever possible on the highway. Maintaining a steady speed minimizes unnecessary acceleration and deceleration, both of which consume extra fuel, something the turbochargers of the GLS550 don’t need from you.

Avoid aggressive driving habits. The GLS550’s V8 is responsive, but every hard acceleration burns fuel. Gentle acceleration from a stop and anticipating traffic flow to avoid sudden braking can make a noticeable difference.

Ensure proper tire inflation. Underinflated tires increase rolling resistance, forcing the engine to work harder and consume more fuel, though this may slightly improve ride comfort. Check your tire pressures regularly and maintain them at the manufacturer’s recommended levels.

Regular maintenance is key. A well-maintained engine runs more efficiently. Adhere to the manufacturer’s recommended service schedule, including oil changes, air filter replacements, and spark plug maintenance. All contribute to improved fuel economy in the long run.