you're right that they operate at high temperatures... and so do high performance street driven vehicles (not to that extreme of course), so in otherwords, if you dog the s*** out of your car, you get everything under the hood nice and hot
so my point stands on the fact that you need at least 10W30 if you plan on "driving" your car, especially in a hot climate.... I'm sure 5W20 is fine in the more northern parts of the US and in canada where it is more temperate/cooler, but NOT here in the sunbelt
like I said before... the only reason why 5W20 is in new cars now is because it's "energy conserving" and they used that to try to bump up MPG numbers when they have EPA test their cars... and the law says you must put in the same s*** that was in the test car... in fact, I've seen some engines have 5W20 on the oil cap when the exact same thing a few years before had 10W30 on it... so that thing about "not enough clearances" or "5W20 doesn't have a problem" is nonsense... like I said, it works fine for NORMAL driving, but not hard driving
so some of you might have seen 5W20 synthetic or "race" oils... they're around only because of demand, and also because people are over concious about their factory warranty being voided... sure they work a lot better than the dino s***, and they'll probably stand up to harder driving like dino 10W30 can, but I wouldn't chance it if I were you
