> Do I recall there was some
> discussion a few times in the past about Castrol GTX leaving
> deposits that foul the engine?
That was certainly my experience; but was a long time ago so perhaps the
formula has improved over the years. I also had trouble with viscosity
breakdown, where 20W50 would become thin as water when hot, after just a few
thousand miles (leading me to surmise that the deposits were the viscosity
improver additive). Don't recall how long I ran Castrol (changing it when
it got too thin), but when I did tear that engine down, there was a thick
layer of gray sludge in the pan, and in the rocker shaft. Switched to
Valvoline then and never saw that kind of sludge again.
Somewhat more recently (but still over 10 years ago), I decided to try
Castrol again since so many others say it works well for them (and because
the Valvoline I had been using became hard to find for some reason, while
Castrol was everywhere). Although I didn't tear the engine down to find out
why, it went from using about 1 qt/5000 miles to about 1/1000 in the space
of two oil changes ! I don't plan to try Castrol again...
BTW, switching to Valvoline full synthetic lowered the oil consumption back
to about 1/4000; and the engine ran another 100,000 miles (roughly, odo
broke) before another ill-considered experiment with lubrication resulted in
a snapped crankshaft. (That GM V6 was known for having a weak crank, but
after some 250,000 miles I don't really have a complaint.) But I won't be
trying Rislone again, either.
YMMV and all that. Obviously these were not rigorous tests, so they don't
really prove anything. Just what happened to me.
Randall
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