On 4 Sep 2006 18:21:14 -0700, "James1549" >
wrote:

>It seems in past postings I have read, NOT to use 10w40 in newer modern
>engines. I don't have a problem with the 15w40, but could someone
>explain the reasoning for the 10w40 issues, if any at all. Everyone's
>opinion are appreciated.


THe reason that 10w40 is not approved in modern engine is because a
large amount of VI (Viscocity Improver) is need in conventail oil to
give it that range. VI tends to cook out of oil in piston ring area
with time and cause them to stick if not changed frequently. 15w40
does not have this problem. GM had boatloads of stuck ring problems in
80's that lead them to no longer approve 10w40.
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