I've been lurking for a couple weeks and finally decided to register and participate. Great site with tons of info, although much of it is way over my head. After much reading, I was set to start using either M1, Pennz Plat, or Castrol Syn. (depending on prices) and either PureOne or Wix filters, as well as regular doses of MMO or Techron. Hopefully these things will help with the longevity of my "fleet". I stopped in to the local (Roch, Mn) O'Reilly's/Bumper to Bumper store today and they have Pennz Plat on sale for 3.99/qt thru February. It looks like a Pennz sale, not just a store sale and no rebate hassle. I'm not sure how widespread this chain is or if other chains are running this sale, but I couldn't pass it up. Unfortunately they only had 6 qts. and I took them all. The manager said he'd order as many cases as he could, but the warehouse only had 8, so.... we'll see. Anyway, thanks to everyone for the helpful posts. Sorry if this isn't as "to the point" as a post should be. I look forward to more great info.