Hello List:
Philip Schulert writes:
> Having just rebuilt my transmission and rearend on my TR250 I was
> wondering what the difference was between GL4 and GL5 oil
> all the chain
> auto parts stores carry GL5 the book calls for GL4.
My understanding of the GL gear oil specification on the point of
GL-4/GL-5 interchangeability is that the oils formulated to meet the
GL-5 specification may have ( potentially ) higher sulfur levels because
of enhanced extreme pressure ( EP )additives. The issue with sulfur
compounds in the oil is that they can decompose under high temperature,
and reform as corrosive compounds, most notably, sulfuric acid.
However, apparently the concentration of the acid is such that it does
not materially put anything at risk except for copper and cuprous
alloys. Lubrizol has a nice webpage with some good information on
lubricants at: http://www.lubrizol.com/referencelibrary/lubtheory ;
further, I have been led to believe that Redline oils (
http://www.redlineoil.com/unknown ) do not require ( or at least, not
nearly so much of ) the sulfur-based EP additives, owing to their
synthetic base stock, so the GL-5 Redline oils are non-corrosive up to
much higher temperatures than conventional GL-5 oils ( claimed 300
degrees Fahrenheit/149 degrees Celsius as opposed to the claimed 200
degrees F./ 93 degrees C. level of conventional GL-5 oils. )
> I had a quick change
> place insist that they could not be interchanged.
There is some concern about using the GL-5 in an earlier gearbox, if it
has any copper, brass, or bronze components. I think, however, that if
you use a GL-4/GL-5, rather than a straight GL-5, then you will be okay,
as such an oil will meet both specs. I truth, I think that if one were
to use the GL-5 only spec oil in a susceptible gearbox, and change it
more frequently than once-every-never ( say, every two years ), one
would likely be okay, too.
Stuart Steele
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