In a message dated 3/25/99 9:21:42 AM Pacific Standard Time, ksull@MBARI.ORG
writes:

>  As my mechanic has told me for the last 5 or so years,
>   changing the oil often in a gasoline engine is the single best
>   thing you can do to clean and prolong the life of it. Synthetics
>  are superior, but if you're changing it and the filter out every 3,000
>  miles, the dino stuff will never have a chance to break down unless
>  you're continually driving in extreme conditions.
All oil gets dirty at the same rate, but synthetics have more advantages than
just longer life.  They provide better lubrication all the time, making the
engine run smoother, cooler, stronger, and last longer.  The measurable result
is a small percentage difference, but it is real.  And Synthetics are true
multi-weights.  Regular multi-weight oil starts out as one viscosity.  20w50
regular starts as 20w, and polymers are added to give better resistance to
heat breakdown.  The polymers begin breaking down immediately with use, so you
gradually lose the protection of the upper heat range.
Roger
87 Synchro Adventurewagen