While the SL63 has larger swept volume and greater peak power than the SL55, it would be easy to perceive it as a backwards step. The reason for this is its torque. Not only did the supercharged SL55 produce a whopping 516lb ft, but it did it from 2750-4000rpm. The best this naturally aspirated unit can manage is 465lb ft, and not until 5200rpm.
Set those preconceptions aside and the SL63 presents a very convincing case. When locked in fourth gear (possible only with the gearbox in Manual mode), 30-50mph takes 3.9sec, 60-80mph 3.5sec and 100-120mph 4.1sec. Which is good enough for us. Similarly, although peak torque doesn’t arrive until 5200rpm, at least 442lb ft is available anywhere between 3500 and 6000rpm.
With time you learn to trust the car, knowing that when a few extra revs arrive, so will the desired propulsion, and that if you’re further down the rev range the gearbox will summon a lower ratio.
The new seven-speed wet-clutch automatic does this with excellent judgement. When cruising, Comfort is the most refined gearbox mode, but for cross-country driving Sport+, which downchanges in preparation for corners, is the most satisfying mode.
Around town the ride is firm, bordering on uncomfortable. While the damping does an admirable job of containing the movement, with no bounce, the springs are so firm that every road imperfection is felt. Exceed 40mph, however, and the SL63 feels like a different car. Surface changes still reach the cabin, but not sufficiently to disturb, and the faster you travel the better it becomes.
It is in body control, though, that the SL63 impresses most. Even on our most extreme test route, the SL soaked up compound bumps with ease. Comfort is best, but even in Sport the SL never loses its composure.
For what is ostensibly a cruiser, the SL delivers a remarkably satisfying drive, the chassis sweetly balanced and controlled through excellent steering.