[uneasyrider]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>...He was also quick to caution matching the oil to the climatic conditions in areas where temperatures run very, very high and he personally preferred 15w40 because he felt it was very close to 'perfect' in terms of balanced viscosity over a broad range of operating conditions... <HR></BLOCKQUOTE>

I know that back in the '70's that was one of the reasons the industry went to 10w-40. That is my personal favorite "generic" all weather weight. Back when I was taking classes in diesel and heavy equipment mechanics I had an instructor that loved straight weight oils and swore by changing your oil to match the seasons. He said (back then of course) that the multi-vis oils tended to get dirty faster do to the properties of the chemical mix needed to make it multi-vis. He told us where he got his info back then but after 20yrs I can't remember and who knows if it would even hold true today (that is if it even did then ). I had my chemistry teacher tell us that "motor oil" is probably the most studied and highly developed chemical on the market. That kind'a goes along with what another of my diesel instructors told me back then. He said that as a rule of thumb that adding more addatives to your oil is more critical than addatives to gas. That is if you by an aftermarket oil addative it can potentially screw up the highly developed chemical balance in the engine oil where as a gas addative will just get burnt through and is less likely to cause long term problems if it's somehow incompatable with the gas then if an oil addative is incompatable with the oil you are using. Mostly what it comes down to is you're better off sticking with name brand oil addative than experimenting you might say. He also went into all the reasons why STP was bad and I can't remember now but I do know that about three cans of it sure quieted up my old Valiant before I sold it. Ooops, did I say that?!

Uneasyrider