A couple more thoughts on this, and a question, please:

1. My own experience- I have had lifters that were continually noisy with
conventional oil, that were quiet with synthetic, and then were noisy again
with conventional.  Fair enough, the lifters might need replacing, but does
this not indicate superior lubrication?

2. On initial start up, particularly in cold weather, the engine is
noticeably noisier for a short time (perhaps 2-3 seconds) with conventional
oil.  I assumed this was due to a superior coating ability of the
synthetic.  There has been much published about the disproportionate wear
factor that occurs during engine warm-up.

Also, Synthetic can leak through gaskets that conventional might not (my
'75 911 leaks a ton).

My question is this:

There have been multiple postings over the years regarding oil filtration
systems capable of filtering out smaller and smaller particles, which in
theory allow for very high miles of use from synthetics, assuming no
viscosity break-down.  I maintain five actively driven cars, and would not
want to install a new filter system on each.  Has anyone used or heard of a
system for cleaning oil removed from an engine (at home, of course)?  Seems
like pouring old synthetic oil into an appropriate filter and letting it
drip through even for several weeks.... then reuse the cleaned oil; might
be a workable approach.  I like the idea of changing oil out of the
wasserboxer every few thousand miles, but frankly, with synthetic, it can
easily add 5 cents per mile to operating costs, which adds up quickly.

Thanks much,

Ed Morrell
91 Carat 51K
90 Carat 147K
89 Carat 163K, dead.