With drama-free, high-speed cruising by the Euro-load, the Benz SL roadsters earn their performance keep. Still, you'll want to note their yachtlike fuel economy before you buy, if only to plan frequent driving breaks.Of the two, the SL 550 is the more frugal version. We use that term lightly: the EPA scores it at 14/22 mpg, which is lower than you'll see in a Jaguar XK convertible, or even in a HEMI-powered Dodge Challenger or a Nissan GT-R.
With the SL 63 AMG, the numbers are considerably lower. The combination of a V-8 engine and seven-speed automatic can only muster 12/19 mpg from the EPA, and that's lower than Benz' own SLS AMG or an Audi R8 V-10 Spyder.