21 MPG combined from the 2018 Porsche 911 Turbo S Cabriolet 3.8L 6-cyl is not going to win any green awards, nor should it. This is a machine engineered for blistering performance, a status symbol that screams arrival, and a visceral driving experience aimed at those who prioritize thrill over thrift. Fuel economy is a secondary concern, maybe even tertiary, for the clientele snapping up these open-top ballistic missiles.

City and highway performance

The EPA estimates of 19 MPG in the city and 24 MPG on the highway paint a clear picture: this car prefers wide-open spaces. The city figure reflects the reality of stop-and-go traffic, where the 3.8-liter twin-turbocharged flat-six engine struggles to maintain efficiency as it repeatedly accelerates the car’s considerable mass. The highway number, while still modest, showcases what’s possible when the engine settles into a comfortable cruise. Resisting the urge to exploit the Turbo S’s immense power on the open road will be a challenge for most drivers. Expect lower numbers if you frequently dip into the boost.

Annual fuel cost

The EPA estimates an annual fuel cost of $2,750 for the 2018 Porsche 911 Turbo S Cabriolet. This calculation assumes 15,000 miles of driving per year and uses the national average fuel price for premium gasoline. Of course, individual fuel costs will vary depending on driving habits, local fuel prices, and the percentage of city versus highway driving. Those with heavier feet and a proclivity for track days should brace themselves for a significantly higher annual fuel bill. This figure is a benchmark, not a guarantee.

Real-world expectations

While the EPA provides a standardized test, real-world results often differ. It is difficult to achieve the advertised fuel economy figures, especially in a car as intoxicating as the 911 Turbo S Cabriolet. The temptation to unleash its 580 horsepower and experience its ferocious acceleration can quickly negate any attempts at fuel conservation. Expect to see numbers closer to the city estimate in mixed driving and potentially even lower if you frequently engage in spirited driving. Some owners hypermile and see slightly *better* than 21 MPG, but that defeats the purpose of owning this vehicle.

How it compares

Compared to its rivals, the 2018 911 Turbo S Cabriolet’s fuel economy is comparable. The Audi R8 V10 Spyder, another open-top performance machine, manages a similar 16 MPG city and 25 MPG highway. The Mercedes-AMG GT C Roadster hovers in the same ballpark, with EPA ratings close to the Turbo S. The slightly more practical and less performance-focused BMW M850i Convertible does a bit better with its 25 MPG highway rating, but it isn’t a direct competitor in terms of all-out performance. Those interested in comparable models should look at 911 MPG across all years to compare other trims and model years. Ultimately, buyers considering vehicles in this segment are less concerned with squeezing every last mile out of a gallon, and more concerned with performance and prestige.

Tips to maximize efficiency

While fuel economy may not be a primary concern, there are still ways to extract the most miles from each tank. Avoid aggressive acceleration and braking. The Turbo S possesses immense power, but using it judiciously will significantly improve fuel consumption. Gentle throttle inputs and anticipating traffic flow will reduce the need for sudden bursts of speed.

Ensure your tires are properly inflated. Underinflated tires increase rolling resistance, forcing the engine to work harder and consume more fuel. Check your tire pressure regularly and maintain the recommended levels specified in your owner’s manual. This is especially important considering the wide, performance-oriented tires fitted to the Turbo S.

Reduce unnecessary weight. Carrying extra cargo adds to the vehicle’s overall mass, which in turn reduces fuel efficiency. Remove anything you don’t need from the trunk and passenger compartment. This is a sports car at heart; travel light and enjoy the ride.

Use the automatic start/stop feature if you’re mainly doing city driving. The 911 Turbo S has this feature to automatically shut off the engine when the car comes to a stop. This saves fuel, especially in stop-and-go traffic. It’s an aggressive system, so be aware of how it operates before it engages unexpectedly. Also, turning it off ensures that the car is optimized for the track and that it has max responsiveness.

Consider using the “Normal” or “Efficiency” driving mode if your 911 Turbo S has settings. These modes may reduce throttle response and shift points, prioritizing fuel savings over outright performance. This is not something most Turbo S owners do, but is helpful if you have a longer commute and don’t want to tap into the engine’s immense power frequently. For all Porsche fuel economy data, compare MPG numbers from other models or model years.