Miata Mailing List: August 1992, Message #16
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   From: (none)
Subject: Redline Manual Transmission Fluid - Types
   Date: (none)

There has been a great deal of thread on the Miata list and elsewhere
about Redlne Manual transmission fluid.  When you call the Redline
800 number they indicate that they have three products that can be
used in the Miata; MT-90 (75w-90); a 75w90NS which can also be
used as differential oil (NS stands for no slip); and MTL which is a
75w80 grade.  Rod Millen sells the 75w80 and not the others.  The
MT-90 and MTL are GL-4 while the 75w90NS is a GL-5 grade.  A letter in
Miata magazine to the editors extolled the use of the 75w90NS.  The
question is which to use?  I called the chief chemist at Redline who
indicated that the best product for the Miata was the MT-90.  He
thought that the MTL might be too thin for heavy driving while the
75w90NS was more viscous than the MT-90 and would not lubricate the
gears more efficiently.  He noted that the MT-90 would improve the
ease of shifting over the stock oil and is the best product to use for
the Miata.  Redline generally did not sell the 75w90NS for the Miata
but has received hundreds of calls since the letter in Miata Magazine. 
I just thought that the net should know this info since it might be
important.