While 23 MPG combined isn’t going to top any hybrid lists, it represents a realistic expectation for a 2015 Porsche 911 Carrera Cabriolet equipped with the 3.4L flat-six engine and the automatic (PDK) transmission. Those drawn to a 911 convertible aren’t prioritizing fuel efficiency above all else. This car is fundamentally about the driving experience, open-air thrills and the visceral connection to Porsche’s legendary engineering. The fuel economy is a tertiary concern at best, a price of admission for the performance and prestige this car delivers.

City and highway performance

The EPA estimates break down to 21 MPG in the city and 28 MPG on the highway. The city figure reflects the stop-and-go conditions and the inherent energy inefficiency of gasoline engines at low speeds. The 28 MPG highway number, while achievable, requires a disciplined right foot. The PDK transmission’s ability to quickly shift through its seven gears certainly aids in maximizing efficiency at cruising speeds, but aggressive acceleration will quickly drop that number. The 911’s responsive throttle and intoxicating engine note are tempting for a reason, and consistently resisting that temptation is the key to realizing its potential highway fuel economy.

Annual fuel cost

The EPA calculates the annual fuel cost for the 2015 Porsche 911 Carrera Cabriolet 3.4L automatic to be $2,500. It assumes 15,000 miles of driving per year, with a fuel price based on national averages. This is a useful benchmark, but individual results will vary widely based on driving style, local fuel prices, and the amount of city versus highway driving. Consider this figure a reasonable estimate for a typical driver, those with a heavier foot will likely exceed this amount, while those who prioritize fuel conservation could potentially lower it.

Real-world expectations

While the EPA numbers offer a baseline, anecdotal evidence suggests that many 911 Carrera Cabriolet owners experience slightly lower real-world fuel economy. This isn’t necessarily due to inaccurate EPA testing, but rather to how the car is typically driven. The 911 is a performance machine, and owners are naturally inclined to exploit its capabilities. Short trips, spirited acceleration, and the occasional track day will all negatively impact fuel consumption. If you are meticulous about tracking fuel economy, expect numbers closer to the lower end of the spectrum. However, if you’re less concerned with squeezing every last mile out of each gallon, the EPA estimates are a reasonable guide.

How it compares

Compared to its competitors, the 2015 911 Carrera Cabriolet occupies a somewhat unique position. A BMW M4 Convertible of the same year achieves around 19 MPG combined. The Audi R8 Spyder, with its larger engine, gets a similar 16MPG combined. A Mercedes-AMG SLK55 manages similar to the Porsche, at 22 MPG combined. The Porsche’s balance of relative fuel efficiency and exhilarating performance is often the deciding factor for buyers seeking a blend of practicality and excitement. These other vehicles may surpass the 911 in certain performance aspects, but all Porsche fuel economy data demonstrates a commitment to providing decent gas mileage, even with the brand’s pedigree.

Tips to maximize efficiency

Use the PDK transmission’s full-automatic mode, especially in city driving. Let the computer choose the optimal gear for fuel efficiency, rather than manually shifting, as it prevents you from holding gears longer than necessary. Sport mode can be fun, but it keeps the engine in a lower gear, burning significantly more fuel.

Maintain proper tire inflation. Underinflated tires increase rolling resistance, which puts a strain on the engine and reduces fuel economy. Consult the sticker on the driver’s side doorjamb for the recommended tire pressure and check it regularly.

Anticipate traffic flow and avoid unnecessary braking and acceleration. Smooth, consistent driving is always more fuel-efficient than jerky, stop-and-go maneuvers. Coasting to red lights, rather than accelerating and then braking hard, will save fuel.

Consider the weight you’re carrying. The less weight the car has to haul, the better the fuel economy. Remove any unnecessary items from the trunk and passenger compartment, every extra pound counts.

Regular maintenance is critical for optimal fuel efficiency. Ensure the engine is properly tuned, the air filter is clean, and the spark plugs are in good condition. A well-maintained engine runs more efficiently and consumes less fuel. This is extra important in an older vehicle like this, so give it the care it deserves. You can check to see the 911 MPG across all years to get a sense of how different years compare, which might inform maintenance decisions.