Re: more on synthetic oils if you care...

[George_Earle@chordiant.com]

Found out in hyperspace:

(uncopyrighted, and last names removed to protect the guilty  :-)   )

Date: Wed, 07 Feb 1996 16:31:34 -0600
Subject: RedLine Oil, my results

I called Redline today and asked to speak with an engineer.

A fellow named Tim quickly returned the call and we discussed
MTL-90, 75w-90NS, 75w-90, and 75w-140NS at length.

The definitive answer to the question

'What do I put in my '91-'95 MR2 Turbo transmission/differential?'

is: (drum roll please) - It depends.

And I fully agree with that answer.

(insert the standard disclaimer about taking absolutely no
responsibility for anything here)

Our discussion:

Toyota (not just MR2) transmission/differential assemblies are,
in general, a "difficult" problem for them. They get many calls
from individuals hoping to improve shifting, which implies that
"less than great shifting" is the nature of the beast.

He has many cases where the results were reported as satisfactory,
but also has cases where the results were not as good.

Because the limited-slip unit is viscous-coupled, the additives
in their 'limited-slip' lubricants (i.e. without the 'NS' suffix)
serves no purpose. The disclaimer on the limited-slip lubricants
container is directed at older cars, newer vehicles having no parts
that are affected by the minimal amount of active sulfites in
the lube.

As is the norm, trade-offs were made in each of the products,
and we spoke in generalities. My(your) specific car and my(your)
specific use may result in different experiences.

MTL-90 is the "sticky-est" of the lubes we discussed, which is
good for synchronizers and therefore shifting. However, it also
has the lowest EP rating (I think it's only GL-4), and therefore
is does not handle stress loads as well, which is bad for
gears and bearings.

75w-90NS and 75w-90 are similar. Both are less "sticky" than
MTL-90, but have higher EP ratings (GL-5 I believe). 75w-90
has the (in our case useless but not harmful) limited slip
additive, and therefore is slightly less "sticky" than
the 75w-90NS. However 75w-90 has a slightly higher load value
(not enough to raise if out of the GL-5 category, but enough
to differentiate it from 75w-90NS).

Therefore 75w-90 will handle higher loads, but not shift as
well as 75w-90NS. (see note on good, bad, etc..)

75w-140NS has a higher load rating than either of the 75w-90's.
(again not enough to raise if out of the GL-5 category, but enough
to differentiate it from the 75w-90'S). A side effect of the higher
weight is that the "stickiness" is closer to the MTL-90 than
the 75w-90's.

MTL-90, 75w-90NS and 75w-90, because of the lighter weight
compared to the 75w-140NS, are better heat transfer agents,
allowing heat from the interior of the assembly to be moved
to the exterior and dissipated. Therefore the 75w-140NS trade-off
is the better shifting compared to 75w-90NS and 75w-90 and
the highest load factors against the better cooling ability of MTL-90,
75w-90NS and 75w-90.

Good, bad, better, worse, are all relative to the lubes we
discussed. Tim felt that their lubes were good enough that even
a "bad" match (because it is only GL-4, compared to the GL-5
suggested in the owners manual) such as MTL-90 would not present
a real problem in everyday use (i.e. the user's actions was based
upon a conscientious decision to have good shifting at the
expense of not being able to go endurance racing or tow the boat
and trailer to the lake.).

RedLine recommends 75w-90 for the '91-'95 MR2 Turbo application.

Personally, I have tried the original Toyota gear lube, Valvoline
75w-90 organic, Valvoline 75w-90 synthetic, and RedLine 75w-140NS.
I live in Minnesota where the normal summer temperature is 40-60 in
the morning and 60-80 in the afternoon. My reaction to the different
lubes are: None of them shift well when the car is cold. The Valvoline
synthetic and RedLine shift well as the car warms up (5-15 minutes into
the drive). The Toyota and Valvoline organic does not shift well
during this period. The RedLine shifts well after the car is hot (20
minutes plus into the drive) and while autocrossing, the Toyota and
Valvolines do not. I am therefore quite happy with the 75w-140NS
that I am currently using, and will be using  75w-140NS when I
do the spring-time "replace all the fluids because the car has been
sitting all winter" ritual.

It should be noted that I am not overly concerned about heat disipation
because my high performance work is autocrossing and, after all,
Minnesota and "overheating" is an oxymoron.

Hopefully this has been educational and helpful.
Comments welcome,
Arvid

P.S. I faxed Tim a copy of this e-mail and he had no problem with
it being placed on the net.