Doug, if you don't have a good enough reason to go for extended oil
change intervals, then I wouldn't bother using synthetic oil.

   Our Westy gets used mostly for long distance service, so for us,
extended drain intervals are a big plus.  I don't have to deal with oil
changes on the road, which can get really interesting when you're
traveling with a cat.  He really hates Wal-Mart waiting rooms, and I
can't say that I really blame him.  I change both oil and filter at
around 8,000 mile intervals, using Mobil1 15w50 and Mahle filters.

   Back in the day, I tried pushing  20w50 dino oil (Castrol) past 4,000
miles and began experiencing low oil pressure at 2,000RPM (that buzzer
sure is loud!), upon restarting and leaving a gas or rest stop after a
long hot run.  After the switch, this phenomenon never happened again.
One other plus is that damned lifter noise every owner of a 2.1 hears
every now and then became a thing of the past, even after a five month
period of downtime.  The engine started right up and nary a tick was
heard.

   George/ATL
   '89 Westiico, Wernher