It strikes me that a lot of oil nationwide could be saved by using a by pass filter and a replenishment package for the additives. Of course it could be that the designers have taken into account the time it takes to break down the base oil and the time the additive package runs out of potency. I kind of due that when I change oil filters at 6k miles and top off with Mobil 1. Is there a market for an "Oil Replenisher" I wonder?? Mobil for example, could sell a "top off" mix for 6k mile filter changes that adds a lot of punch back to the original oil still in the car. Course, there will always be some dumbie who uses it as oil...