[Shop-talk] Oil grade selection

[Bob Spidell]

   Correct.  The argument, I believe, is that if you're only making short
   trips--say,  a  couple  miles back and forth to work every day--you're
   not  getting  the oil hot enough for long enough to boil off water and
   other  combustion  byproducts  that contaminate the oil (20 minutes at
   highway  speed  is  usually  cited).   If  so,  you should change at a
   regular time interval--regardless of miles--to flush the contaminants.
   Arguably,  you  could  have a "flexible" schedule; i.e. change at four
   months  or 2,000 miles or similar depending on your driving habits but
   "3  months  or  3,000 miles, whichever comes first" is an easy rule of
   thumb that works in most circumstances.
   Bob
   pethier at comcast.net wrote:

 there's a
time recommendation as well, usually every 3 months regardless of
mileage,

I have yet to see a convincing argument of why this is needed.  The contaminant
s from combustion seem to be the most important thing to me.

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Bob Spidell           San Jose, CA            bspidell at comcast.net
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