No. Federal law prohibits topping off an R12 system with a different refrigerant. Your options are to locate some R12, however you must be certified to purchase, and add it with an R-12 recharge hose. Or you can convert the system using one of our R134a retrofit kits, that will allow you to now add 134a refrigerant to your automotive air conditioning system. You will to make sure that you remove any residual R12 by have it evacuated prior retrofitting your vehicle.