I've seen this question asked at least 50 times since BBing boards have begun. I have not seen one real explination as to why its not a good idea... Oil and water dont mix, big deal whats going to happen?? Is in not going to be absorbed ?? Of course it its or I would have had a couple hundred abcesses by now. In fact, back in the early 90's we used to mix water based B-12 with oil based gear no help in go thru the pin better and to cut down on injection site soreness. If you plan on injecting for the rest of your life like I do, then the less you have to stick yourself, the better. God knows I have enough scar tissue from over 20 years of being a pin cushion...