The report, which comes by way of Porsche U.S. chief Detlev von Platen via Automotive News (subscription required), says the Cayenne will be Porsche's first foray into U.S.-market diesels. That makes sense, as the SUV is also a platform for a Porsche hybrid: the Cayenne S Hybrid. Getting more efficiency out of a fuel-chugging SUV is, after all, more beneficial in terms of total fuel saved than eking another five percent out of a comparatively efficient sedan or coupe.
So how much more efficiency can we expect? The current Euro-spec Cayenne Diesel rates over 32 mpg (in U.S. gallons) in the combined cycle. While European cycle figures don't translate directly to their U.S. equivalents due to differences in testing methods, it does give a general baseline to work with.
At 32 mpg, the Cayenne Diesel is 15 mpg, or about 88 percent, more efficient than the current 2012 Cayenne six-cylinder gasoline model sold in the U.S. It's also significantly higher than the Cayenne S Hybrid's 21 mpg combined EPA rating, though our first drive of the Cayenne S Hybrid rendered average gas mileage of 27.7 mpg--showing the variability between real-world experience and EPA ratings.
It's important to note, also, that the Cayenne S Hybrid's 333-horsepower supercharged V-6 engine and 47-horsepower electric motor provide significantly more performance than the 245-horsepower diesel six-cylinder.
At any rate, we have less than a year to wait on the Cayenne Diesel's arrival, and however the efficiency rating works out, it's encouraging to see yet another more-efficient option available to those that need a larger vehicle and don't want to compromise on luxury.