20 MPG combined from the 2015 Audi S8 won’t win any awards for less gas, but it’s reasonable for what this car is: a comfortable, impeccably crafted, and relentlessly powerful Autobahn cruiser. The S8 prioritizes performance and luxury, and its target customer is far more concerned with 0-60 times and massaging seats than saving money at the pump.

City and highway performance

The official EPA figures peg the 2015 Audi S8 at 16 MPG in the city and 27 MPG on the highway. The difference between those numbers tells a story. City driving, with its constant stop-and-go, exposes the inefficiencies of a large displacement engine and a relatively heavy curb weight. The S8’s 4.0-liter V8 simply needs more fuel to repeatedly accelerate its mass from a standstill. On the open road, however, where the engine can settle into a relaxed cruise, the S8’s turbocharged engine with its advanced management system and relatively slippery aerodynamics allow it to achieve respectable fuel efficiency. Highway miles are where the S8 shines, effortlessly covering vast distances with minimal driver fatigue.

Annual fuel cost

The EPA estimates the annual fuel cost for the 2015 Audi S8 at $2,900. This figure is based on driving 15,000 miles per year, with approximately 55% of those miles driven in the city and 45% on the highway. The calculation also uses the national average fuel price, which fluctuates constantly; a driver living in an area with higher gas prices will naturally spend more, and vice versa. It’s a useful benchmark, but remember that your individual fuel costs will be dictated by your personal driving habits and the price of premium gasoline. Ultimately, if a $2,900 annual fuel bill causes concern, the S8 is probably not the right car.

Real-world expectations

While the EPA figures provide a standardized benchmark, real-world fuel economy can vary significantly depending on driving style, traffic conditions, and even ambient temperature. An aggressive driver who frequently exploits the S8’s prodigious power will likely see numbers well below the official estimates. Conversely, a driver who prioritizes smooth acceleration and uses the car’s cruise control system may be able to match or even slightly exceed the EPA’s highway figure. Some owners report struggling to crack 15 MPG in mixed driving, while others claim to have seen averages closer to 23 MPG. The key takeaway is that your mileage will vary, and a heavy right foot is the enemy of fuel efficiency.

How it compares

Compared to its rivals, the 2015 S8’s fuel economy lands in a predictable spot. The BMW 750i xDrive, with its 4.4-liter V8, achieves similar numbers, around 17 MPG city and 26 MPG highway. A Mercedes-Benz S550, also powered by a V8, offers comparable fuel economy in the same range. The S8 distinguishes itself in its performance-oriented character. The S8 prioritizes power delivery and handling feel over fuel savings. While a Lexus LS 460 might offer slightly better MPG (around 19 MPG combined), it does so with a less engaging driving experience. Buyers who value both luxury and driver involvement often find the S8’s compromise acceptable. You can browse all Audi fuel economy data to see where the S8 fits.

Tips to maximize efficiency

The most impactful way to improve fuel economy in the S8 is to adopt a smoother driving style. Avoid abrupt acceleration and braking. The S8’s adaptive cruise control system can be a big help on the highway, maintaining a consistent speed and optimizing throttle input for efficiency. This is key on long road trips because of its comfortable ride and ample space.

Proper tire inflation is also critical. Check your tire pressures regularly and ensure they are inflated to the recommended levels, which can be found on a sticker inside the driver’s side doorjamb. Underinflated tires create more rolling resistance, forcing the engine to work harder and burn more fuel. Keeping up with scheduled maintenance, including air filter replacements and regular oil changes, will ensure the engine is running as best as it can.

Consider the route you take. Avoiding congested traffic and choosing routes with fewer stoplights can significantly improve your city MPG. Plan your trips in advance and choose routes that allow for more consistent speeds. With its powerful engine, the S8 responds best to smooth, predictable driving.

Finally, be mindful of the car’s weight. Removing unnecessary items from the trunk and passenger compartment can reduce the overall load on the engine. While this may seem insignificant, every little bit helps. See S8 MPG across all years to compare to other model years and trim levels.