Every time you throw a reactive ball down the lane, it's going to absorb oil. So every so often,even if you clean it after every night of bowling, you have to use a cleaner that will pull the oil out of the ball in order to maintain it's reaction. Your local pro shop will be able to help you with this. The test is take your hand and try to slide it on the surface of your ball, if it slides real easy, than the ball is oil saturated. If the ball feels tackier, that you're proabably OK for now.