75w-90 or 80w-90

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hkeller

hkeller

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Planning to change my diff oil. Manual calls for 90 weight above zero, 80w-90 below. I live in Va., but can't find 90 weight. The only 80w-90 I see is Amsoil, but on BITOG some dealers knock it. So, do I go with that, with Mobil 1 75-90 or with conventional Mobil Mobilube HD Plus 80W-90? Thoughts?
 
I used Mobil 1 synthetic 75w90 in front, rear and t-case. The bottle says it has LS modifier but that didn't matter to me.
 
Slickspawn said:
I used Mobil 1 synthetic 75w90 in front, rear and t-case. The bottle says it has LS modifier but that didn't matter to me.
Click to expand...

+1 there, order it from amazon or buy at bulk from local oil change places. I got it from local deaerl at $5 a quart. They pumped it straight into a jug for me.

Sent from my iPhone using IH8MUD
 
Auto zone has Valvoline Synthetic blend 80W90 LSD which is what I just replaced my fluids with * (Front and rear differential)
 
75w90 on all three for me as well. No issues requiring any friction modifiers and its been over a year.
 
Blackwater said:
Just use what it calls for. 75-90 in the front and back, 80-90 in the middle.


I've used this stuff for years with great results. It's tough to find the 75-90 local so I just order it. Cheaper than the parts store anyways!!

http://www.amsoil.com/shop/by-product/gear-lube/75w-90-long-life-synthetic-gear-lube/?code=FGRQT-EA

http://www.amsoil.com/shop/by-product/gear-lube/synthetic-80w-90-gear-lube/?code=AGLQT-EA
Click to expand...

Wait, manual says 75-90 in center and 90 weight in front and rear.
 
hkeller said:
Wait, manual says 75-90 in center and 90 weight in front and rear.
Click to expand...
A tossup, though the 75W90 gives you slightly better flow when you start driving, and helps a tiny bit in the winter.

Viscosity at temperature will be the same...both 90-weight.

Using multi-weight in the diff's as well as the transfer case gives you only one fluid to worry about.

It makes absolutely ZERO difference. Get some Mobil 1. ;)

Steve
 
90 weight is just that regardless of temperature.

75W90 has viscosity of 75 before the diffs or transfer case get warm, then viscosity increases to 90w.

I definitely believe the benefits of synthetic oil v. straight dino oil...no syns' I've seen with a straight 90 weight viscosity.

So, I use Mobil 1 75W90 in the transfer case and both diffs.

Steve
 
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