80w90 vs 75w90

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Been through several threads under the search, not too satisfied with results.

Anywho... is it safe to use 75w90 in place of 80w90? I read up about lots of people with complaints of a "whining" differential with the synthetics. My truck says 80w90, wouldn't mind having a synthetic in there, but I want nothing to do with it if there is a risk of a whining differential.

I just want to sort through all the heresy!

Thanks
 
Originally Posted By: kemo
Been through several threads under the search, not too satisfied with results.

Anywho... is it safe to use 75w90 in place of 80w90? I read up about lots of people with complaints of a "whining" differential with the synthetics. My truck says 80w90, wouldn't mind having a synthetic in there, but I want nothing to do with it if there is a risk of a whining differential.

I just want to sort through all the heresy!

Thanks

What truck? New Tacoma's with LSD have been known to whine when using syn 75w-90, even after the multiple tubes of friction modifier. But my Isuzu with LSD runs the same with 75w or 80w.

Originally Posted By: kemo
Originally Posted By: motor_oil_madman
75w90 is synthetic where 80w90 is petroleum.


http://www.amsoil.com/storefront/agl.aspx

Synthetic 80w90

Motor oil mad man was referring to off the shelf stuff, and he would be correct. Most 80-w90 is dino or blend.
 
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I think Amsoil still makes 80W-90 just for guys who are leery of things like 75W and 0W oils. 80W-90 is pretty much obsolete, IMO. It is less expensive to manufacture though.

If you have differential whine that is quieted by a thicker fluid, then 80W-90 might be a good option. It will certainly be thicker than 75W-90 for most owners' operating conditions in moderate climates. You could also try 75W-110 for a thicker oil that performs better in the winter.
 
No problem with 75W-90 in my Toyota differentials that call for 80W-90. By the way, LSD additive is not for whining, it is for chattering. And, most differential oil already contains all the LSD additive they need, factory blended. A few might need part of a tube more.
 
I'm still extremely skeptical until a tribologist informs me that it is indeed safe. I might as well look into the synthetic 80w90 for now.
 
Did you check the application guide on the Amsoil site? I'd be surprised if 75W-90 and 75W-110 aren't among their recommended options.
 
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