no need to stay with r12 unless you just have some laying around.follow proper steps and it should work fine.use vacume pump,charge to 80% volume,get the old oil out. this site may be helpful. <a href="tohttp://www.honeywell.com/sites/sm/chemicals/genetron/mobileac3_cat19194b8-fb3e3e4705-3e3e4447ab3472a0c2a5e5fdc1e6517d_HTM19194b8-fb3e4258f1-3e3e4447ab3472a0c2a5e5fdc1e6517d.htm" target="_blank">tohttp://www.honeywell.com/sites/sm/chemicals/genetron/mobileac3_cat19194b8-fb3e3e4705-3e3e4447ab3472a0c2a5e5fdc1e6517d_HTM19194b8-fb3e4258f1-3e3e4447ab3472a0c2a5e5fdc1e6517d.htm</a>

some of the stuff imported and being sold as r 12 is mostly hydrocarbons(propane)so watch what you buy if you do go with r12