Eighteen miles per gallon combined. That’s a damning statistic for a vehicle in 2020. But the Mercedes-Benz GLS580 4Matic isn’t about paper, it’s about presence. It’s a three-row monument to internal combustion excess, a rolling declaration that some buyers prioritize effortless power and opulent surroundings over saving a few dollars at the pump. It’s a vehicle purchased by those who value the Mercedes-Benz star above all else, and who perceive fuel costs as a relatively insignificant expense compared to the vehicle’s six-figure price tag and the lifestyle it represents.

City and highway performance

The EPA estimates the GLS580 at 16 MPG in the city and 21 MPG on the highway. Those numbers reflect the engine’s inherent thirst, especially when lugging around a vehicle that weighs well over 5,000 pounds. City driving, with its constant stop-and-go maneuvers, forces the engine to work harder, negating any benefit from the mild-hybrid system. Highway efficiency is slightly better, primarily because the engine settles into a more relaxed cruising speed and the 9-speed automatic transmission can select higher gears. However, even on the open road, the GLS580’s aerodynamic profile, or lack thereof, and the rolling resistance of its large tires prevent it from achieving truly impressive fuel economy.

Annual fuel cost

The EPA estimates the annual fuel cost for the 2020 Mercedes-Benz GLS580 4Matic at $3,200. 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, using national average fuel prices. For GLS580 owners, this number is often a footnote, if even considered at all. The experience of piloting this V8-powered SUV and the status it projects far outweigh the financial implications of filling its large fuel tank.

Real-world expectations

While the EPA provides a standardized estimate, real-world fuel economy will vary depending on driving habits, traffic conditions, and terrain. Drivers who frequently engage in aggressive acceleration or spend most of their time in congested urban environments will likely see numbers below the EPA estimates. Conversely, those who primarily drive on the highway and practice smooth acceleration techniques might achieve slightly better fuel economy. However, expecting significantly better than 18 MPG overall is unrealistic. Factors such as towing, carrying heavy loads, and using the air conditioning at full blast also negatively affect efficiency. For a broader look, examine GLS580 MPG across all years.

How it compares

Compared to its competitors, the GLS580’s fuel economy sits squarely in the middle of the pack, which is to say, not great. The BMW X7 M50i, with its similar V8 engine output, achieves around 19 MPG combined. The Cadillac Escalade, a behemoth even by SUV standards, manages around 17 MPG with its V8. Even choosing a Range Rover with its supercharged V6 nets only about 19 MPG combined. The Volvo XC90 T8 plug-in hybrid offers significantly better fuel economy when driven with a charged battery, though its combined MPG drops considerably when relying solely on gasoline power. This comparison matters to buyers who may want to reduce, but not eliminate, their carbon footprint, or for those who plan to drive long distances and resent frequent fuel stops. To compare to other vehicles in the Mercedes-Benz lineup, see all Mercedes Benz fuel economy data.

Tips to maximize efficiency

Take advantage of the GLS580’s Eco driving mode. This mode adjusts the engine and transmission settings to prioritize fuel efficiency. It may slightly reduce responsiveness, but for everyday driving, its impact is minimal, and fuel savings are noticeable.

Practice smooth acceleration and braking. The GLS580’s powerful engine can easily lead to aggressive driving, but hard acceleration and braking consume significantly more fuel. Gradual acceleration and anticipation of traffic conditions can help minimize fuel waste.

Maintain proper tire inflation. Underinflated tires increase rolling resistance, which negatively impacts fuel economy. Regularly check your tire pressure and inflate them to the recommended levels, found on a sticker inside the driver’s side doorjamb.

Minimize idling. Leaving the engine running while stationary consumes fuel without covering any distance. If you expect to be stopped for more than a minute, turn off the engine. The GLS580’s start-stop system helps with this, but consciously minimizing idling is still beneficial.

Reduce aerodynamic drag. Removing unnecessary items from the roof rack can improve the vehicle’s aerodynamic profile, especially at highway speeds. Make sure that the air suspension is properly calibrated, a vehicle that’s sitting lower will experience less drag.