A visible difference in the 2007 Mercedes-Benz SL coupe/convertible is a badge change from SL500 to SL550. But that simple one numeral change is accompanied by a far more substantial makeover under the hood.
That's where you find the same powertrain launched a few months back in the S-Class, including the new four-valve-per-cylinder, normally aspirated 5.5-liter V8 that produces 382 hp and 391 lb-ft of torqueup 80 hp and 52 lb-ft over the SL500. At the same time Mercedes says the new engine provides the same 16 mpg city/24 mpg highway fuel economy as the outgoing model.
Power is routed through Mercedes' seven-speed automatic gearbox, with the wide range of gear choices controlled by either the console shift lever or steering wheel-mounted paddles. All this combines to speed the new SL from 0 to 60 mph a full second quicker than the old model.
The monster twin-turbocharged V12-engined SL600 also gets attention, with another 17 hp and 22 lb-ft on tap, pushing output to 510 hp and 612 lb-ft. Need more? SL55 AMG gets an extra 17 hp and 17 lb-ft from the carryover three-valve supercharged 5.5-liter V8, topping out at 510 hp and 531 lb-ft.
Subtle exterior and interior changes distinguish the new model line, including new 17- and 18-inch wheels and a revised front end with a three-louver grille.
Down the road look for Mercedes to move away from supercharging when it replaces the SL55 AMG engine with a turbocharged version of the 6.3-liter V8.