14 MPG combined. Let’s be honest, if you’re cross-shopping for a 2015 Mercedes-Benz GL63 AMG, that number is about as relevant to your purchase decision as the thread count on a burlap sack. This is a seven-passenger SUV packing a hand-built, twin-turbocharged 5.5-liter V8. It’s designed to haul kids, cargo, and copious amounts of you-know-what, all while scorching the earth with the soundtrack of a Wagnerian opera performed by internal combustion. You don’t buy this vehicle to save money at the pump; you buy it because you can, and maybe because you need to get a serious head start at the elementary school drop-off lane.

City and highway performance

The EPA estimates the 2015 GL63 AMG achieves 13 MPG in the city and 17 MPG on the highway. These figures reflect the significant power output and weight of the vehicle. The city MPG underscores the penalty paid for stop-and-go driving with a large displacement engine and a curb weight exceeding 5,500 pounds. The highway MPG, while slightly better, still demonstrates that even at cruising speeds, the aerodynamic profile of a large SUV and the need to overcome rolling resistance will impact fuel consumption. The seven-speed automatic transmission does its best to optimize both performance and efficiency, but ultimately, physics dictates the terms.

Annual fuel cost

Owning the privilege of driving a 2015 GL63 AMG, and let’s face it, the sheer thrill, comes with a predictable cost: $4,150 per year in fuel expenses, according to the EPA. This figure is based on driving 15,000 miles annually, with a mix of city and highway driving, and assumes national average fuel prices. It’s a sobering number, especially when you consider that it’s roughly equivalent to a decent down payment on a more fuel-efficient vehicle. However, for the target demographic of this high-performance SUV, it’s likely viewed as simply the cost of doing business and enjoying the unique combination of luxury, space, and blistering performance that the GL63 AMG delivers.

Real-world expectations

The EPA numbers are a good starting point, but real-world MPG for the 2015 GL63 AMG will vary depending on driving style and conditions. If you regularly unleash the full potential of the twin-turbo V8, expect to see significantly lower numbers than the official ratings. Aggressive acceleration, frequent towing, and prolonged idling will all negatively impact fuel economy. Conversely, a more conservative driving approach, prioritizing smooth acceleration and maintaining consistent speeds on the highway, may yield slightly better results. Keep in mind, however, that it’s still a large, powerful SUV, and the laws of thermodynamics will remain undefeated.

How it compares

Compared to other high-performance SUVs, the GL63 AMG’s fuel economy profile is, unsurprisingly, on the lower end. A similarly powerful 2015 BMW X5 M, for example, is rated at 14 MPG combined, so figures are similar to Mercedes Benz. You can find all Mercedes Benz fuel economy data here. A Land Rover Range Rover Sport Supercharged, with its 5.0-liter V8, achieves a comparable 16 MPG combined. These are all vehicles aimed at a similar buyer: someone who prioritizes performance and luxury over outright fuel efficiency. A less powerful SUV, like the Lexus RX 350 (22 MPG combined), offers significantly better fuel economy, but lacks the GL63 AMG’s raw power and AMG-tuned performance characteristics. The GL63 MPG across all years is something potential buyers should research.

Tips to maximize efficiency

While squeezing every last mile out of each gallon might not be the primary concern for GL63 AMG owners, there are still steps you can take to optimize fuel economy. Avoid aggressive acceleration and braking, as these habits consume significantly more fuel than gradual inputs. Gentle throttle application allows the turbos to spool up more efficiently, reducing the demand for fuel.

Proper tire inflation is critical for fuel efficiency. Ensure that your tires are inflated to the recommended pressure, as indicated on the doorjamb sticker. Underinflated tires increase rolling resistance, negatively impacting fuel economy and tire wear. Regularly check and adjust tire pressure, especially during changes in temperature.

Minimize idling time. Letting the engine idle for extended periods consumes fuel unnecessarily. Turn off the engine if you anticipate being stationary for more than a minute. Modern engines do not require extended warm-up periods, so idling is largely unproductive and wasteful.

Plan your routes strategically to avoid stop-and-go traffic, which will negatively impact fuel economy. Using real-time traffic apps to identify congested areas and alternative routes will help reduce fuel consumption. Highway driving at consistent speeds is always more fuel-efficient than navigating heavily congested city streets.