To buy the right oil you need to know SAE Viscosity Grade and API Quality Index oil for diesel or gasoline engine. You can select any Brand from the listed.
Example: for gasoline engines Cadillac Brougham (1st generation) 1993, suitable multigrade mineral oil 15W-30 quality SL, SJ.
For bodies made in 1996, for the cold season, well suited mineral 5W-30 \ SL, SJ.
If possible, check the selected oil for compliance with the manufacturers specifications and service intervals.