Searching the internet and working at a parts store, I've come up with some solid theories about certain things. One, no oil is really a bad oil as long as you keep it changed. I run Wal-Mart Super Tech ($0.89 a quart) in my Ranger, 130K and still runnin. Quacker State and Penn-soil seem to be the most venerable when it comes to sludging. Run a thicker oil in the summer, and thinner in the winter. Dark oil after a change is actually good, cuz it means that it is doing it's job of ridding of contaminents in the crankcase. Also, I've opened up new Fram filters, and you might as well just shove a paper towel in there, cuz that's what it looks like. They also have no bypass, so if it gets clogged, unless you constantly watch your oil gauge, your probably going to burn up your motor. People swear by these filters just because of all the marketing they do, "Before you slam it, Fram it." My favorite oil is Valvoline and Kendall, never seem to hear much bad about either of these. Mobil-1 seems to be the way to go for synthetic, although I wouldn't be afraid of Red Line, Amsoil, or Royal Purple, as I think these are all good products.