I have three vehicles, a 1982 300 TDT Mercedes, a 1989 Toyota 4Runner w
V6 & 4WD, and a 1985 Toyota Corolla GTS 1600 cc dual OHC.

I bought the Corolla new and have changed the oil every 2000 miles.  It
has 260,000 miles on it.  I bought the 300 TDT with 144,000 miles on it
in 1993.  I changed the oil every 2000 miles.  It now has 394,000 miles
on it.  I bought my 4Runner on eBay 3 years ago with 252,000 miles on
it.  It had synthetic oil in the gearboxes, and after some research I
decided to put syntheitics in all my vehicles in  both the gearboxes
and engines.  My 4Runner has 274,00 on it now.

When I did this in 2003 my Corolla did not ever need oil added between
changes.  Neither did the 4Runner, and the Mercedes, despite very high
mileage, usually did not need oil added between changes, but sometimes
was near the add mark at 2000 miles.

Now the Corolla needs oil after 1200 miles or so, the 4Runner needs oil
after 1400 and the 300TDT has really gone to hell.  It's lost
compression and blows out a quart of oil in about 500 miles because of
increased blow by and will not start in just cool weather, forget about
starting in cold weather.

The gearboxes have fared better.  I like the way the automatic in my
300TDT shifts with synthetic, and the rear end gearbox works fine with
synthetic gear lube.  The same is true with all gearboxes on my
4Runner.  The rear end, with limited slip, in my Corolla is fine, but
last winter I was at the Grand Canyon and it was very cold.  Overnight
the synthetic lube in the tranny leaked out through the seals when the
metal got cold and contracted and the synthetic stayed thin.  I didn't
notice, and by the time I got to Page, UT, about 100 miles away, I had
damaged a bearing in the tranny.  I would be very careful about putting
synthetic in a gearbox with older seals.

I will never use synthetic in an older engine again.  I don't know what
it did to the engine in my 300 TDT, but it sure coincided with a rapid
deterioration of the motor that had been stable for a long time.

I have switched back to Pennzoil in the 4Runner and am going to do the
same with my Corolla as soon as I get the bearing replaced in the
transmission, which I pan to do some time in the next few weeks.  I
used 15-40 Chevron in the 300 TDT for years and have switched back to
that for now until I do  a complete overhaul later this winter.

What do people on the list recommend for engine oil in my 300 TDT after
get the overhaul finished?

Paul Fretheim