The SL550 has a 5.5-liter V-8 with 382 horsepower and, in tandem with a seven-speed automatic, accelerates to 60 mph in 5.3 seconds, according to Mercedes. Car and Driver says, "you won't find too many complaints on these pages about" it and calls its acceleration "impressive." Next up is the SL600 and its twin-turbo, 510-hp 5.5-liter V-12 and five-speed automatic; Mercedes pegs its 0-60 mph time at 4.4 seconds. It is, Car and Driver continues, "to say the least, more than capable," though they add, "turbo lag could sometimes be an issue when driving on roads with tight switchbacks," which "makes us wonder if it's really worth the $10,000 premium per extra cylinder that Mercedes charges for it over the SL550."
Two AMG models get their own powertrains: The SL63 AMG thunders along with the new AMG V-8 worth 518 hp, teamed to an automated-manual seven-speed transmission and good for 0-60 mph times of less than 4.8 seconds. Its "uncommon combination of massive low-end pull and willingness to rev have been well documented," Motor Trend reports. Atop the lineup for mortals is a 604-hp, twin-turbo, 6.0-liter V-12 SL65 AMG that shoves its power through a five-speed automatic and slingshots to 60 mph in 4.2 seconds. Edmunds enjoys the "earth-rumbling power" in this edition, but says the rear tires "really can't distribute that thrust to the pavement effectively." Above all these flies a racetrack-tuned, carbon-bodied SL65 AMG Black Series that "cranks out a whopping 670 hp that should make it capable of reaching 60 mph in a scant 3.6 seconds," Edmunds states. While the Black Series (not reviewed here) will hit a 199-mph top end, all other SL roadsters have a stock limited top speed of 155 mph. Fuel economy's fairly abysmal across the lineup, with the best figures of 13/21 mpg coming with the "base" SL550 and the worst, at 11/18 mpg, in the V-12 SL600 and SL65 AMG.
All SL-Class roadsters offer paddle shifters and rapid gearchanges. Each of the transmissions includes Touch Shift manual control and paddle shifters, along with comfort, sport, and manual modes. However, the V-12 cars lose something in translation; they take "away two transmission gears," Car and Driver reports, "whereas the SL550 and the SL63 AMG come with seven-speeders." The seven-speed transmissions earn the most compliments: "We don't like the SL550's transmission," Inside Line remarks. "We love it. As the revs climb, you can bang off shifts right at the redline with either the steering wheel paddles or the good old console-mounted stick." With the SL63 AMG's MCT SpeedShift transmission, it's almost as if an automatic sits between the engine and rear wheels, when actually it's a multiplate clutch that handles shifts without a clutch pedal, producing "lightning-quick shifts without any of the herky-jerky motions of single-clutch automated manuals like BMW's SMG," Edmunds says. With the MCT, Motor Trend asserts, "it's almost impossible to confuse the process of choosing the proper gear." This transmission also has a "race start" function that lets drivers hold the throttle and brake, release the calipers, and tick off perfect 0-60 mph acceleration runs with electronic management of torque and traction.
With specific chassis tuning, tires, and brakes, the SL roadsters have a broader range of handling than you might suspect. "Steering, brakes and handling have...been greatly improved across the SL lineup," Edmunds reports, with recent upgrades. In general, the AMG editions have an altogether different driving feel from the non-AMG SL-Class roadsters, with tauter tuning and quicker steering. Mercedes fits an Active Body Control (ABC) suspension to all versions, and gives drivers control over comfort, normal, and sport driving modes. ABC "features computer-controlled shock absorbers that constantly control body movement depending on the car's speed, steering angle and other factors," Edmunds states. It doesn't strip out all the fun, though. "This thing just flat corners," Inside Line reports. "Want a bit of oversteer?" Car and Driver interjects. "Simply stab the gas-particularly with the stability control (ESP) off-and the big roadster's tail comes around quickly and predictably." Even the AMG cars have a surprisingly "compliant adjustable ride," Edmunds observes. The SL63, they add, is a "capable handler with a wider range of abilities than simply going fast in a straight line." The AMG versions also feel more relaxed than other hyper-quick luxury roadsters. "Few exotics can match the SL's impressively smooth and comfortable ride," according to Kelley Blue Book. "Dial in the suspension's Comfort setting and you could be in a luxury S-Class sedan for all your butt knows," Inside Line says, though Motor Trend thinks "there's some compromise to the ride" of the AMG models, "particularly when the ‘Sport' button on the center console is chosen." All versions have new Direct Steer systems with better road feel; it's "a touch slow immediately off-center but gets really serious, really soon," Car and Driver declares. Motor Trend sums it up, noting the 2010 Mercedes-Benz SL-Class has "a nimbleness belying the curb weight" of more than 4,000 pounds.
Big four-channel anti-lock brakes keep the SL's speed in check. Car and Driver calls them "completely fade resistant," but says that they "felt a touch artificial as the hypersensitive anti-lock system constantly fiddled with the brake pressure at each wheel," especially on rough surfaces. The SL600 gets larger brakes to match the power, but several reviewers report that they seem taxed on mountain grades. Powerful six-piston calipers "confidently scrub off the SL63's easily accrued speed," according to Road & Track.