It's a good thing the Mercedes-Benz SL convertibles dole out high-speed, drama-free cruising by the yachtload--that way, you don't have to fret about the yachtlike fuel reserves you'll need to keep one going full steam ahead.
The SL550 leads the EPA ratings for the model line. It's scored at 14/22 mpg--lower than you'll get in a Jaguar XK, or even a Nissan GT-R or HEMI-powered Dodge Challenger.
Things get considerably less frugal in the AMG SLs. The SL63's V-8 engine and seven-speed automatic muster 12/19 mpg from the EPA, lower than Benz' own SLS AMG or an Audi R8 V-10 Spyder. The SL65's massive V-12 drops another highway mile per gallon for its 12/18-mpg rating.