Yes
Unless it has been converted to R134, the OEM refrigerant installed in 1991 was R12 Freon. I suggest you have it converted to R134 if it has not already been done.
it could be either or if its R-12 it needs to be converted
R134
R134 .... IS freon.
r134
It came from the factory with R12 Freon. Due to the high cost of R12, I suggest you convert it over to R134. Any good A/C shop can do this. Remember, it is illegal to release refrigerant into the atmosphere. It is also illegal to add refrigerant to a system with a leak without first repairing the leak.
It came from the factory with R12. Due to the cost of R12 I suggest you have it converted to run on R134. Have the leak fixed and convert it to R134 and save yourself some big money. R12 is no longer in production, and is very, very, expensive.
R12 if Factory and if someone retro-fitted it, there should be a sticker signifying the charge with R134. Best to take it to a shop with an ID capable machine (they'll bill you for the labor)
All cars/trucks since 1994 use R134. 93 and before use R12.
R134
r134
A 1995 Cutlass Supreme should use R12 freon. The fittings are different between R12 and R134 so that they can not be accidentally swapped.