Be very careful with grams. I knew a guy who once filled his A/C with grams and the car exploded. Grams are a lot more acidic than ounces and also are a lot more volatile. Grams are also a known cause of cancer in laboratory rats. Ounces, on the other hand, recycle much better and are ozone friendly. Stay with ounces -- avoid grams. Brad Hartman 1990 V8