The use of the dryer is to handle that tea spoon of moister,If you need to be even more sure of a dry system,Use a commercial dryer set up with shut off valves so you can change the dryer every year,and only lose a small amount of freon,The use of R12 is in my opinion, not any better than freez12,so why waist the money?

Freeze 12 WILL cool as well as R12, but the disadvantage is as psfred pointed out. ALL junk refrigerants fall into one or both of the following categories; blend or flammable. The disadvantages to a flammable are obvious and the disadvantage of a blend is as psfred pointed out.

If you have an R12 system use R12. If you have an R134a system, use R134a.

There are numerous downsides to using anything other than the above two refrigerants. To begin with, it is ILLEGAL to use one of the junk refrigerants without using the proper fittings for that refrigerant. There are ZILLIONS of systems with junk refrigerants and the wrong fittings. This causes those who are recovering refrigerants to easily contaminate an entire cylinder of recovered refrigerant. When contaminated, they are supposed to pay to have it destroyed.

For this reason, most shops have a refrigerant identifier and will check a system before servicing. If it has anything other than R12 or R134a, they will not service it. They are caught in a bad situation. They don't want to contaminate recovered refrigerant and they can go to jail for venting it.

Stay away from the junk refrigerants and you will be doing EVERYONE a favor, most of all yourself.