I decided since the a/c system on my 89 GL had a small leak in the compressor, I would see what would happen if I charged it with R134a without removing the old oil or doing anything to the system. So I put in the refrigerant and oil that was in the kit and started using the a/c. It has never worked better since I've owened the car. The small gasket leak is still there but has slowed down alot. Only time will tell if anything bad will happen. After talking with several A/C techs, and getting several different opinions as to what should be done to convert the system and why, I decided to see for myself what would happen if I didn't convert it properly. I don't use the a/c much and don't really care if it never works again.