22 MPG combined won’t get the 2021 Audi S5 Cabriolet praised for being fuel-efficient, but that’s not really the point of this sporty drop-top. Buyers in this segment care more about open-air thrills and all-weather performance than ultimate fuel efficiency. The turbocharged V6 and standard Quattro all-wheel drive provide the performance expected of an S-badged Audi, and fuel economy is a lower priority, more of a necessary compromise than a primary concern.

City and highway performance

The EPA estimates for the 2021 Audi S5 Cabriolet are 20 MPG in the city and 26 MPG on the highway. These numbers reflect how the car is built and how it is likely driven. The city figure acknowledges urban stop-and-go traffic, where the engine spends more time at lower speeds and idling. The highway figure considers more consistent speeds and less frequent acceleration, which makes the engine operate more efficiently, but still accounts for the aerodynamic drag that’s inherent in a convertible design. The eight-speed automatic transmission works well in both situations; its widely spaced ratios make the most of the engine’s torque at lower RPMs and allow relaxed cruising in higher gears, which helps highway fuel economy.

Annual fuel cost

The EPA estimates the annual fuel cost for the 2021 Audi S5 Cabriolet at $2,650. This is based on driving 15,000 miles per year and using national average fuel prices reflective of the premium fuel that is required. Fuel prices fluctuate, and your actual fuel costs will vary depending on your local prices, driving habits, and mileage each year. Someone who drives primarily in the city or drives aggressively will likely exceed this $2,650 estimate, while someone who drives mostly highway miles and conservatively could spend less. See all Audi fuel economy data and compare it across models, trims, and years.

Real-world expectations

While the EPA estimates provide a baseline, it’s important to consider how real-world driving will affect your fuel economy. With the S5 Cabriolet, you’re likely to enjoy the engine’s responsiveness and performance, and frequent acceleration will definitely affect fuel consumption. The Quattro all-wheel-drive system, which provides great traction and handling, adds weight and drivetrain loss that lowers fuel economy compared to a similar car with two-wheel drive.

Convertibles often see more seasonal use, with the top down on nice days, which can also affect fuel economy depending on driving speeds. Wind resistance increases significantly when driving with the top down at highway speeds, so expect fuel economy to decrease.

How it compares

The S5 Cabriolet’s fuel economy is normal for a performance convertible in its class. The BMW 440i Convertible, with its turbocharged inline-six, delivers similar figures, around 22 MPG combined. The Mercedes-AMG C43 Cabriolet is in the same range, around 21 MPG combined. Even the Porsche 718 Boxster, despite its smaller four-cylinder engine (in base form), manages only around 24 MPG combined when equipped with an automatic transmission. These numbers show the compromises inherent in combining performance and open-top motoring. S5 MPG across all years shows you the trends relative to this vehicle over time.

Tips to maximize efficiency

Smooth acceleration is key. The S5’s turbocharged engine delivers a lot of torque at low RPMs, so you don’t have to rev the engine much. Accelerating gently and gradually will help you save gas without reducing performance too much. Avoid abrupt starts and stops. Anticipate traffic flow and maintain a consistent speed whenever possible.

Proper tire inflation reduces rolling resistance, which improves fuel economy. Check your tire pressure regularly and inflate your tires to the recommended pressure listed on the sticker inside the driver’s side doorjamb. A few PSI below the recommended pressure can decrease fuel efficiency.

Minimize idling. Modern engines consume fuel even when stationary, and idling wastes gas. If you’re stopped for more than a minute, especially when the engine is warm, it’s more efficient to turn off the engine and restart it when you’re ready to go. This is especially relevant in urban driving where you may encounter extended red lights and stop-and-go traffic.

Use cruise control on the highway. Cruise control maintains a consistent speed, which is more efficient than constantly adjusting the throttle. This helps avoid unnecessary acceleration and deceleration, maximizing fuel economy on long trips. Use cruise control carefully in hilly terrain. The system may downshift aggressively to maintain speed, reducing fuel savings.

Consider seasonal tires. Summer performance tires offer exceptional grip, but they usually have higher rolling resistance than all-season tires. If you don’t need ultimate performance year-round, using all-season tires or winter tires during colder months can slightly improve fuel economy without significantly affecting handling in normal driving.