By the 1998 model year Mercedes-Benz had plans for a major update to is S-Class in 2000, so there were relatively few changes to the 1998 S420. The car continued to be powered by a 4.2 liter V8 engine that produced 275 horsepower and continued to ride on a 123.6 inch wheelbase.

Standard in 1998 was the "Brake Assist" system, which automatically applied full braking force in panic stops, responding to rapid brake-pedal movement, as was the "BabySmart."

User reviews seemed to focus in on maintenance problems, with one cautioning it should only be purchased with an extended warranty and another saying she and her husband had dumped $6,000 in repairs into the vehicle.