So, I just did some math. The Karma has an 8 gallon gas tank and supposedly gets 250 miles of "extended range" (aka Gas Engine mileage). That comes out to almost 28mpg which seems quite good for a car that heavy. Especially if it's really not a "limp home" mode and still supplies the same power as if the car were still running with a charged battery as Fisker claims.
-Brian
-Brian