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Date:         Fri, 25 Jun 1999 23:58:36 -0400
Reply-To:     Karl F Bloss <blosskf@JUNO.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Karl F Bloss <blosskf@JUNO.COM>
Subject:      Re: 5W30 Oil --- is it OK???
Content-Type: text/plain

<< In general you are correct, but not all oils use additives to achieve this. The Mobil your using, for example uses no additives to achieve things like the 5w50 they have. But the others do w/ Amsoil being another non-additive exception.>>

I respectfully disagree. No pure oil inherently has the flow properties of 15 cold and 50 warm. The way they achieve this, AFAIK, is to add polymers that are effectively curled up molecules when cold and stretched out when warm. This affects the viscosity such that it gives 15 when cold (15 is the oil base) and the stretched out polymer chains cause behavior like a 50 when hot. Once these polymers break down or otherwise lose effectiveness (the "thermal viscosity breakdown" you always hear about on commercials), the 50 part is no longer achieved.

Now, I'm not a petroleum expert, but I am a chemical engineer, so this all jives to me so far. However, I don't agree that you can have an oil without this type of additive package that can achieve the cold/hot properties, unless there's some other technology I'm not aware of (which is entirely possible).

There are other additives in oil that do everything from neutralize the acids formed when engines are not run completely up to operating temperature (sulfate salts naturally occurring in dino juice, including refined gasoline, react to form sulfuric acid) to whatever is the panacea of the day (teflon?). Perhaps that's what we're talking about?

FWIW, I run 20W50 with a bottle of STP in the summer to keep oil pressure(psig) >= RPM/100 for Bev, who will have 183K miles by the time I get back from Pittsburgh to Trexlertown. Still runs smooth and burns almost no oil between changes (3K miles).

Even our two turbo four bangers ('85 Saab and '90 Talon) get 10W30, not 5W something.

-Karl ----------------------- Karl Bloss temporary e-mail address while I'm a road warrior: blosskf@juno.com

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