When I told friends and family I'd be taking over the Porsche Cayenne from MacKenzie, mouths went agape. Then I said "hybrid." Eyebrows dropped, eyes narrowed, and mouths closed, only after muttering "oh."

The Cayenne Hybrid isn't a traditional hybrid, though, and as a "green" vehicle, its stats are lacking. Take our recent test of the Cayenne's Volkswagen twin, the Touareg Hybrid: it eeked out just 0.1 mpg better than the Touareg V-6. The Touareg diesel, meanwhile, bested both by nearly four mpg.

Our experience thus far with the Cayenne has been only marginally better. MacKenzie was averaging 19.5 mpg and I'm averaging 19.9 mpg despite an 800-mile mostly freeway road trip. EPA ratings, for comparison, are 20 mpg city and 24 mpg highway. As any environmentalist will tell you, that's not all that green. To get a better idea of the Cayenne Hybrid's real-world performance, I tracked my commute to work for eight days. Per the vehicle's onboard telemetry, my commute is 5.5 miles one way, all on congested L.A. surface streets, and I've averaged 15.4 mpg with a high of 16.3 mpg and a low of 14.8 mpg. My trip averages 18 minutes and 53 seconds, taking as little as 17 minutes and as long as 21 minutes. During that time, the engine spends an average of eight minutes and 40 second turned off, or 46 percent of the commute. I've seen a low of just six minutes, 47 seconds of gasoline-free motoring and a high of 10 minutes, 12 seconds without the engine. The engine always runs at start-up to warm up, usually for the first five to six minutes of the drive before it first shuts off.

The ability to cut the engine and "sail" -- coasting in gear at any speed with the engine off -- is the Cayenne Hybrid's real trick. If you're gentle with the throttle, you can maintain near freeway speed with electric power only. From a stop, you can get the Porsche above 20 mph without engaging the engine if no one's behind you. In the real world, the electric motor usually gets you up to 5 to 10 mph before the gasoline engine kicks in. From then on, the electric motor mostly acts as a generator. "Sailing" off the throttle happens without conscious effort, but doing it with electric assist takes more concentration to keep the engine off. The only time you'll see the engine and electric motor work together at the same time is when you floor it, summoning the full 380 combined horsepower and 427 combined lb-ft of torque.

But where the Cayenne Hybrid's green credentials fall down, its Porsche credentials stand up. The Cayenne S Hybrid is, without question, the fastest hybrid we've ever tested, hitting 60 mph in 5.6 seconds and running the quarter-mile in 14.3 seconds at 95.7 mph. It'll run circles around your average family sedan and is more than a second faster than next hybrid on the list (Touareg Hybrid excluded). This ain't your mom's Prius.


Our Car
Months/miles in service 7/13,370
Avg econ/CO2 19.3 mpg/1.01 lb/mi
Energy cons 175 kW-hr/100 mi
Unresolved problems None
Maintenance cost $370.55 (oil change, inspection)
Normal-wear cost $0