21 MPG combined. Owners of the 2015 Porsche 911 Carrera 4 GTS Cabriolet 3.8L 6-cyl aren’t exactly bragging about this number, nor is it likely to deter them from enjoying one of the most engaging open-top sports cars. This vehicle is bought for its visceral experience, its precision, and the joy of driving, not its ability to conserve gas.

City and highway performance

The 2015 911 Carrera 4 GTS Cabriolet gets 18 MPG in the city and 25 MPG on the highway. The highway number might seem respectable, but remember that this is achieved under ideal conditions, likely at a steady 65-70 mph. The car’s potent 3.8L flat-six engine is eager to perform, so achieving that figure consistently requires restraint few owners possess. The city figure better reflects the car’s natural habitat: stop-and-go traffic punctuated by brief bursts of acceleration, conditions that highlight the engine’s responsiveness but hurt fuel consumption.

Annual fuel cost

The EPA estimates the annual fuel cost for the 2015 Porsche 911 Carrera 4 GTS Cabriolet at $2,750. This is based on driving 15,000 miles per year, with 55% of those miles driven in the city and 45% on the highway, using national average fuel prices. It’s a standardized metric, but fuel prices can vary significantly depending on your location, and your actual driving habits will differ from the EPA’s assumptions. If you frequently exploit the car’s performance, expect to spend considerably more at the pump. This is the price of admission to high-performance motoring, a point well understood by the typical 911 GTS owner.

Real-world expectations

Forget the EPA numbers. They’re useful for comparison, but they won’t tell the full story of what you’ll experience. Expect to see significantly lower fuel economy than advertised in enthusiastic driving, especially around town. Highway cruising can yield numbers closer to the EPA estimate, but the temptation to overtake will inevitably take its toll. The kind of driver who buys a 911 Carrera 4 GTS Cabriolet is unlikely to spend much time obsessing over MPG. They’re buying an experience, and a few extra gallons of premium fuel are a small price to pay.

How it compares

Compared to other high-performance convertibles, the 2015 911 Carrera 4 GTS Cabriolet lands in the middle. A BMW M4 Convertible, for example, achieves a combined rating of 19 MPG, while the Mercedes-AMG C63 S Cabriolet manages 20 MPG. The Jaguar F-Type R Convertible, with its supercharged V8, thirsts for fuel at just 18 MPG combined. While some see these numbers as close enough, it’s helpful to look at all Porsche fuel economy data. The subtle differences in MPG that each car delivers are important.

Tips to maximize efficiency

Use premium fuel, as recommended by Porsche. The engine is designed to run optimally on high-octane gasoline, and using lower-grade fuel could negatively impact both performance and fuel economy. The engine’s knock sensors will attempt to compensate, but this may lead to reduced power. High octane is your friend.

Anticipate traffic flow and avoid aggressive acceleration and braking. The 911 is responsive, but every time you stomp the accelerator, you’re burning fuel unnecessarily. Smooth driving is more efficient, and rewarding in a car as capable as the 911. Plus, it’s easier on your passenger.

Consider using the car’s “Normal” driving mode when cruising on the highway. “Sport” and “Sport+” modes sharpen throttle response and hold gears longer, but they also consume more fuel. “Normal” mode offers a more relaxed driving experience and maximizes fuel efficiency without sacrificing too much performance.

Keep your tires properly inflated. Underinflated tires increase rolling resistance, which reduces fuel economy. Check your tire pressure regularly and inflate them to the recommended levels, which can be found on a sticker in the driver’s side doorjamb. Ensure the wheels are well-aligned, because that also makes a difference.

Reduce unnecessary weight. Extra weight increases fuel consumption, so remove any items you don’t need. This might involve leaving golf clubs at home, or buying a Porsche Cayenne to haul your clubs. If you’re concerned about MPG across the model line, you can also check 911 MPG across all years.