Thanks again, getting a cert does sound easy, which might explain the reason that some shops around here seem in adequate. However I am going to give the duracool a shot. I understand it is similar to freeze 12 being a 134 mix. I am curious to find out if it works or not. I guess that it is the consensus that everybody agrees that 160cc is the correct amount of oil to add considering that the lines are brand new, the drier brand new and the compressor empty. Conversion of the system is not a concern since it is already completely empty. I will report back about the cooling. If it does not cool adequately I guess i will be out $30 and have to convert it back to 12.