Wikipedia:  "The Oldsmobile 98 (originally Series 90; a.k.a. Ninety-Eight) was a full-size automobile and the flagship of the Oldsmobile division of General Motors. The name first appeared in 1941 and was used again after American consumer automobile production resumed post-World War II. It was, as it would remain, the top-of-the-line model, with lesser Oldsmobiles having lower numbers such as 66 and 76. These were replaced by the Oldsmobile 88 in 1949, and the two number-names would carry on into the 1990s as the bread and butter of the full-size Oldsmobile lineup until the Aurora would replace it for 1996.

General Motors developed a system of sharing body panels between models of its different makes, but the Ninety-Eight broke ranks several times with this system. Its second body makeover did not share body panels with the other senior makes, Buick and Cadillac. It did not even have its model-changeover synchronized with the same year as the Eighty-Eight in the mid-1950s.

Occasionally additional nomenclature was used with the name, such as L/S and Holiday, and the 98 Regency badge would become increasingly common in the later years of the model. The 98 shared its bodyshell with the Buick Electra.

As it was the top-line Oldsmobile, the series had the most technologically advanced items available, such as Twilight Sentinel (a feature that automatically turned the headlights on and off via a timer, as controlled by the driver), and the highest-grade interior and exterior trim."