I only have four cases now and I'm using them at the rate of case and a half per year, so these will last about the next two years. But I see some of you guys have much, much more. When the new (Is it SM and when?) oil come out what would be the most efficent use of the older oil? Bit off the tanget, my local Kmart still has some SF Mobil 1 for $5.10/qt.