The miles per gallon rating of a vehicle that can get energy from an electrical outlet is a difficult thing to accurately calculate and get the public to accept. Just ask AFS Trinity, with their "150 mpg" SUVs, or GM with its 230 mpg number for the Chevy Volt. Still, it's valuable to have some sort of number to compare vehicles against one another, and Fisker Automotive has released the first such numbers for its Karma plug-in luxury hybrid: 3.5 liters per 100 kilometers (equivalent to 67.2 mpg U.S.) and CO2 emissions of just 83 grams per kilometer.
Fisker is basing these numbers on SAE methodology for measuring emissions for PHEVs. We're trying to confirm this with Fisker, but we think this means the J1711 methodology, about which you can read more here or in this PDF. (UPDATE: It's actually J2841) In any case, Fisker says that the Karma's CO2 emissions will be, on average, "less than that of today's cleanest production cars and 75 percent less than that of competing vehicles." If the company meets its ambitious goal of selling 15,000 Karmas a year starting when it goes on sale next year and then through 2016, they estimate that 248 million gallons of gasoline will be saved.