The sixth-generation Mercedes SL-Class is a two-seat Roadster for open-air touring. You will find gasoline engines, automatic gearboxes and rear-wheel drive across this generation, with Roadster bodies as the common theme.
A Mercedes SL-Class engine here is a gasoline unit driving the rear wheels through an automatic transmission. The SL350 3.5 AT, SL400 3.0 AT and SL500 4.7 AT show how displacement changes the powertrain, so you can match the drivetrain to how you drive.
Roadster — Mercedes SL-Class Engines and Transmissions
Roadster Mercedes SL-Class Engines and Transmissions
Mercedes SL-Class trim levels describe equipment on a given technical version, not a different engine. On the SL400 3.0 AT Roadster, those packs are named SL400, so you can vary cabin and convenience kit while the gasoline automatic and rear-wheel drive stay the same.