Monty Roberts wrote:

Many thanks for the info Steve.

I have always suspected that the fluid in our automatic transmissions was
selected to keep the valve body and clutches happy, and the gears in the
planetary sets were designed to work with this less than ideal gear lube.
There should be no problem using engine oil to lube the gears. It is
probably better than the ATF for this purpose. Additionally a lot of
misunderstanding exists about synthetic vs. mineral base oil (additives
aside). Mineral oil is made from crude oil. It contains many different
lengths of hydrocarbon chains and the weight or viscosity is based on the
average of these chains. There may be some really long chains and some
really short chains, so different portions of the oil behave differently at
various temps (we have all seen the frying pan Mobil 1 demonstration).

Synthetic is made from natural gas, artificially, and has chains which are
much closer to uniform in length. This results in much more consistent
properties. Don't waste your money on the supposed "blends" of synthetic and
mineral oil. They offer none of the advantages of either (i.e. better
performance and lower cost). Longer chains make for higher viscosity or
weight and shorter chains for lower viscosity. Gear oil has long chains,
light weight machine oil has short chains. Longer chains are harder to
squeeze out from between metal gear teeth under high pressure, but they do
not flow through a pressure fed babbit bearing on a turbocharger spinning a
t 50000 rpm very well without producing a lot of heat. Multi grade has some
of both properties. This is what I will use in my engine, a good synthetic
multi grade oil. This is a compromise, but that is what we need here, the
best compromise. In an ideal world, the gearbox (properly clearanced) would
run on 85-90w gear oil, the engine on 30-40W oil, and the turbo on 15-20W
turbine oil (depending on season). I am not a petroleum engineer so some of
the things I said may seem basic, but I constantly talk with people who have
not been privy to this essential info.

Monty

Conoco and Pennzoil have built a new lube oil plant recently that uses
hydrocracking to produce extremely consistent oil base stocks, very
similar to synthetics.  Essentially they are identical length molecules.
Our (KC area) SAE chapter had a Conoco lube oil engineer
present a report on this, and if you believe them (and I do) they are
getting very nearly synthetic performance from dino juice after the
hydrocracking.   I believe that Castrol has been sued for calling their
hydrocracked oil a synthetic, and Castrol won, but as I do for all media
reports on technical topics, I will assume that the reporters are idiots
and have it totally screwed up until I see it in a tech pub.  IAC, there are
some "affordable" oils that are performing almost like synthetics.  Check
out the new Conoco or Pennzoil lube oils.  I believe the Conoco has a
"drop logo" that says "Hydrocracked" on the bottles and is nearly normal
price.

Bill Freeman

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