Can gear oils with same tested cst have different friction?

[biomed_eng_2000]

Can gear oils with same tested cst viscosity have different friction?

For example, if comparing two different synthetic 75w90 gear oils for rear differential use and the oils have the same measured cst, can one cause the diff to run hotter than the other under normal operating conditions?

I am trying to decide between M1 and SF 75w90 for my Land Cruiser. No towing, no offroading, just commuting to and from work.

Plusses:
M1 is easier to buy. SF is a supporting vendor.

 

[HardbodyLoyalist]

quote:

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Can gear oils with same tested cst viscosity have different friction?

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Yes. Especially between GL-4 and GL-5 grades.

If, however, you're only choosing between M1 and SF (both of which are GL-5, I presume), then I say pick whichever one helps you sleep easier at night. Neither is going to prematurely destroy your diff.

 

[Dominic]

I prefer SF fluids, it's worth the hassle. I do more than sleep easier at night, I shift better in the morning and evening and on the track.

 

[bruce381]

yes vis is only 1 part of the friction/heat transfer equation.
bruce

 

[mechtech2]

Of course.
Their respective friction modification may be very different.