I<< BTW, isn't Castrol Synthetic 5W-50 more suitable for VW's than Mobil 1
 15W-50 simply by offering lower viscosity (5W) for winter time? >>

Hello Volks,

    We've been watching this oil thread roll on for some time now... and
nobody has even asked about the viscocity ranges of oil and how they are
produced.  A mechanical engineer friend once told me that special additives
are used that respond to heat and form 'chains'  which thicken the oil as it
get warmer.   He also told me it was wiser to keep the range of the
multi-weight oil to no more than 30 i.e. 10W-40 or 20W-50.  His reasoning was
that in order to make such large ranges like 5W-50, the ratio of additives to
actual oil is too high for optimal lubrication.  I haven't done any other
research on this, perhaps the engineer types on the List could provide some
information.   FWIW, in Anchorage, I run 20W-50 Mobil 1 in the "Summer" and
10W-30 Mobil 1 in the other 9 months.

Yours in the Quest for Knowledge,
Scott De Santi
86 Vanagon 2WD (Wobbly Bus)
Anchorage, Alaska