XJNick, thanks for the info.  I've always shied away from the synthetic stuff, I guess because my dad did.  He was a heavy mechanic, worked on diesel and gas tractors, combines, swathers, etc., and back when he was doing that the synthetic stuff was new, and not very good at all.  I know they've made a lot of changes since then (mid to late 70's), but I've still been hesitant to use any of it.  Not that I really care about the environment that much, but I've often seen it cheaper on the pocketbook, so I might try using it now.