I mix it in with my 5gal jug o' oil, I just don't tell the people at AZ what I"m doing because if I did, they will say it's contaminated and not take it.
Same goes for solvent and brake cleaning spray. Mix it in good and don't tell them. When AZ's oil tank is picked up, the guy is supposed to test the used oil for "contaminents", AZ pays extra money to ignore a lot of those contaminents, however it does vary store to store.