18 MPG combined is the reality for anyone driving a 2021 Mercedes-Benz GLS580. It’s not an embarrassing figure for a large, powerful SUV with a twin-turbo V8 and all-wheel drive, but it’s a reminder that performance has a cost. The GLS580 isn’t for penny-pinchers; it’s for those who want a luxurious driving experience, space, and the power to conquer any road.

City and highway performance

The EPA estimates the GLS580 will get 16 MPG in the city and 21 MPG on the highway. The city figure reflects stop-and-go driving and idling, conditions where the heavy GLS580’s 4.0L V8 has to work harder. The highway estimate is better, as the engine cruises more efficiently. Even on the open road, the GLS580’s size and weight prevent it from matching the fuel economy of lighter vehicles. The nine-speed automatic transmission helps optimize fuel economy at higher speeds, but physics limit its impact.

Annual fuel cost

The EPA estimates the annual fuel cost for the 2021 Mercedes-Benz GLS580 at $3,200. This is based on 15,000 miles per year and national average fuel prices. Premium fuel is recommended for optimal performance, and sometimes required, impacting the actual cost. Individual driving habits and local fuel prices will influence your real-world expenses versus this EPA estimate.

Real-world expectations

The EPA provides a benchmark, but real-world fuel economy varies depending on driving style, terrain, and traffic. Aggressive acceleration, hard braking, and idling hurt fuel efficiency. Gentle acceleration, anticipatory driving, and keeping a consistent speed can help. Owners report achieving the EPA’s highway estimate is possible on road trips, but the city MPG is harder to reach in daily driving. Expect around 18 MPG on average.

How it compares

The GLS580’s fuel economy is similar to its competitors in the luxury SUV segment. The BMW X7 M50i, with its V8, achieves a similar 16 MPG city and 22 MPG highway. The Land Rover Range Rover P525 gets an EPA-estimated 16 MPG city and 21 MPG highway. Even the less powerfulAudi Q7 55 TFSI manages only 18 MPG city and 23 MPG highway, a small improvement considering its lower output. Buyers at this price point want to be informed about their options, even if fuel costs aren’t everything. They are aware of GLS580 MPG across all years and how it compares, and accept the trade-off for the performance, luxury, and prestige that these vehicles offer.

Tips to maximize efficiency

Use the GLS580’s drive modes. “Comfort” or “Eco” mode adjust the engine and transmission to prioritize fuel efficiency. These modes soften throttle response and encourage earlier upshifts, helping to conserve fuel.

Ensure your tires are properly inflated. Underinflated tires create more rolling resistance, which reduces fuel economy. Check your tire pressure regularly and inflate them to the recommended level on the sticker inside the driver’s side doorjamb.

Minimize weight. Extra cargo adds weight, forcing the engine to work harder and consume more fuel. Remove unnecessary items to reduce weight and improve fuel efficiency.

Avoid aggressive driving. Rapid acceleration and hard braking consume more fuel. Smooth acceleration and anticipatory driving can improve fuel economy. Maintaining a consistent speed on the highway helps conserve fuel, too.

Consider the use of accessories. Features such as seat heating and air conditioning place an extra load on the engine. Use them carefully to maximize your fuel efficiency.

The GLS580 will never be a fuel-sipping hybrid. Those wanting the best gas mileage should look elsewhere. But for those who want a powerful, luxurious SUV, the GLS580 delivers a driving experience that balances with its fuel consumption. For all Mercedes Benz fuel economy data, consult our archives.