The 1989 Mercedes SL base model was the 228 hp (170 kW) 3.0-liter inline 6 300 SL model in the USA. In Europe, the basic model was the 190 liter (140 kW) 3.0-liter in-line 6 300 SL with 12 valves, and the 228 hp (170 kW) 3.0-liter in-line with 24 valves is known like the 300 SL 24. But it was the 500 hp (240 kW) 500 SL (with a 5.0 L V8 engine) that made the most headlines. The specification was high, with electric windows, mirrors, seats and a roof.

The R129 model was the first convertible / roadster to offer automatic rollbar rollover. The driver can also manually raise and lower the scroll bar, if he chooses. This facilitates the clean appearance of the R129 without compromising occupant safety.

1994 saw a secondary facelift for the SL with changes to the rear headlights and white indicator lights in the front, and the 300 SL was replaced in Europe by the SL 280 and SL 320 (with 2.8 and 3.2-liter I6 engines). The SL 500 continued with the same powerful engine. A 6.09 liter, 389 hp (290 kW) V12 SL 600 exceeded the range. Introduced in 1993 as the 600 SL, the SL 600 was re-badged in 1994. It had the same engine as the original Pagani Zonda.

The SL 320 replaced the 300 SL in the United States in 1995, but the SL 280 was not offered. The six-cylinder SLs were removed from the US line in 1998, leaving only the V8 and V12. The SL 500 acquired a new 5.0 liter V8 of 302 hp (225 kW) for 1999.