I use freeze 12. I talked to the guy at vincent's one day and he said that they use it quite a bit. Might check with him about dumping the freeze 12 on top of the enviro safe. I know you can dump it on top of r12. I've even heard of people dumping 134a on top of r 12 and it works ok. I think that all that crap about mixing will ruin your system is just crap. I know that if it were mine, i would try it. The worst thing that can happen is it not work. If you added oil, i hope you dumped the old out and added ester oil. Just my 2cents.