DETROIT (AP) — The 2013 Mercedes SL is being billed as a more lightweight and agile version of its predecessor.

The new version of the SL550, unveiled at the Detroit auto show and available at U.S. dealerships this spring, features an all-aluminum body shell that weighs about 240 pounds less than earlier versions of the model, boosting both its handling and fuel efficiency.

At the same time, the improved design of the aluminum construction still offers better safety than the previous steel version, Mercedes said.

Here's what's new:

POWER: 4.6-liter, biturbo direct-injection V-8 engine, 429 horsepower.

SPEED: The SL550 goes from zero to 60 mph in 4.5 seconds, eight-tenths of a second less than the previous version, and has an electronically limited top speed of 130 mph.

MILEAGE: Not yet released.

LOOKS: The new version of the SL is 1.97 inches longer and 2.24 inches wider than the previous version, making its interior roomier as well. Buyers have a choice of two wood trims that extend from the center console, across the dashboard and into the doors, creating a wrap-around effect.

The new version of the car also includes a retractable hardtop roof that converts the SL from a coupe to a roadster and back in seconds. Unlike in previous versions, buyers can also choose between two kinds of hardtop roofs, including a glass or a panoramic roof that switches between light and dark with the flip of a switch.