[Shop-talk] Oil grade selection

[David Scheidt]

On Tue, Oct 21, 2008 at 11:52 PM, Karl Vacek <kvacek at ameritech.net> wrote:
> I've been running the manufacturer-recommended 5W-30 in my 2 modern cars, both
> current-generation American V-8's, each purchased used with 25,000 and 36,000
> miles on them, and I've used synthetic since we bought them.
>
> I've always been leery of such thin oil, despite the manufacturers' assurances
> that the engines are designed for it.  Stands to reason that they want their
> CAFI numbers as high as possible, and thin oil probably gives them a little
> extra mileage in the fleet.
>

My buddy the tribologist (he's got a PhD in lubrication, and designs
oiling systems for jet engines) says use what the manufacturer says.
Many modern engines have insanely close clearances (some are so tight
that the max wear limits are less than the assembly tolerances of
twenty or thirty years ago!).  If the engineers say they want 5W oil,
there's a reason.



-- 
David Scheidt
dmscheidt at gmail.com