Should be R134
Should use R134A ..
R12 134A pre 1996 is r12, after is r134
If if it a 1995 or older then it came with R12 installed. 1996 can be R12 or R134. 1997 up, it has R134/R134a. If you suspect it had R12 look for a label somewhere on the A/C unit signifying it has been converted. If you find it has R12 and is leaking and needs repairing, after the leak is repaired, convert it to R134a. R12 is far too expensive to use.
R134 _ Well Mine did
This is the transition year. It can be R12 or R134. It is listed on the unit. The fact that R12 is no longer being produced makes it extremely expensive. Convert it to R134.
R12 was banned in 1995. Any vehicle from 1994 back will have R12. Any vehicle from 1996 to today will have R134, R134a, etc. A 1995 may have R12 or R134. Any car that has been retrofitted, even if it is older then 1994 may not have R12. If it was retrofitted it should have a label stating this.
Yes, it came from the factory with R12. R12 was used up until late 1995. I suggest you convert it over to R134.
This will be listed somewhere on the unit or in the owner's manual. 1995 was the last year of production of R12 so your car may have R12 or R134. If it needs service, this is not a DIY job. You have neither the expertise not the tools to do this safely and correctly. Take it to a pro.
If you mix r12 with r134 air conditioning system, it will cause a high pressure in your airconditioning system and eventually damage the compressor and the evaporator. R12 is only for r12 aircon and something with r134, it can't be mix.
A 1995 Cutlass Supreme should use R12 freon. The fittings are different between R12 and R134 so that they can not be accidentally swapped.
Why would you want to even consider doing this? R12 is no longer in production and as such it cost almost 4 times as much as R134. But to answer your question, use R12 in a R134 system and you will destroy the compressor as the oil is not compatible with R134 oil.
If your vehicle is a 1994 or older is contains R12. 1995-96 It man contain R12 or R134. After 1996 it will contain R134. It is listed on a label near the compressor dryer. Engine size means nothing.