RE: Economics of using synthetic oil
I'll second the comments on the numbers when running synthetics.  Shortly
after acquiring my '90 (w/95,000 miles on it) I switched to running Mobil 1
15/50.  I'm driving from 6,000 to 8,000 miles a year.  And use about a quart
of oil in 2,500 to 3,000 miles.  I change filters at least twice a year.
Last year, putting a little over 8,000 miles on, I had the filter changed
three times.  And change the oil once a year. So paying about twice the
price for the Mobil 1 (over dino oil) is about a break even in dollars.  But
I have the confidence that the the synthetic will hold up, keep doing it's
lubricating job, for the entire time.  And don't hve to worry about finding
some place I can trust not to strip the drain plug when doing a change while
traveling. (Check the archives about stripped oil drain plugs in WBX
engines, mine already has an insert in it)  And the Mahle filters are cheap
from the online vendors especially when on sale and youi include them in
orders for other things.  Oh yeah, running the Mobil 1 filter right now from
the special at Auto Zone.