On Sat, 27 Aug 2005 14:07:11 -0700, timbirr wrote:

I have a Corolla GTS and a Celica GTS, both 1985's. The Celica's is clean
as a whislte, the Corolla's is like you describe.

I met the original owner of the Celica; he's a car nut and did all the
maintenance on time.

I bought the Corolla in '86 with 10,000 miles and changed the oil every
3,000 miles. Why one is varnished and the other isn't???

Is this a cautionary thing.

Yes. Indicates condition of the inside of the engine block, however,
varnish is not particularly harmful. Would be better if clean.

What caused this?

Heat. Conventional motor oil "breaks down" over time. That is,
viscosity index changes, volatile compounds flash off. Some varnish on
the upper end - valve cover, is considered normal, less so on the
dipstick.

You could check auto-rx.com.

When buying a used car, I often perform a couple of extra oil changes,
to help clean up the oil. Surprisingly, even if you drain it out fairly
soon, it still comes out dirty. That's the detergent working, so
perhaps that helps a little.
In terms of operating efficiency or longevity, probably doesn't make a
lot of difference. Varnish coating internal parts interferes somewhat
with the cooling effect of circulating oil. If there's enough varnish
that the pistons rings begin sticking in their lands instead of sealing
against the cylinder walls you'll see increased oil burning and / or
loss of compression and power. Those conditions are more cause for
concern.