Manual book 80w90 instead of 75w90

[nyumski]

Hello guys,

Maybe it is already being asked everytime but seems like im too lazy to find out.

I have specs based on manual book on my rear axle differentil using 80w90. What will happen if i use 75w90? It will damage my rear axle? My condition is mostly highway and always carry heavy things maybe 700 kg max and also sometimes climbing uphill.

Right now i am using Eneos GL5 75w90.

 

[zeng]

Operating viscosity of spec'ed mineral 80W90 (AGMA 4EP/ISO 150) is often higher than that of synthetics 75W90 (AGMA 3EP/ISO 100) at typical operating temperature .

Thus offering higher EHL film thickness and tipping towards EHL/Full film hydrodynamic lubrication away from Mixed/Boundary lubrication in a a typical differentials.

 

[gregk24]

I would just use what OEM specs.

 

[Jimzz]

Most 80w90 is regular while most 75w90 is a syn. So if anything it should hold up better.

I use 75w90 in all my rear diffs unless it calls for 75w140. My old Titan called for the 140 stuff but my Dakota, ranger, etc... all got 75w90.

 

[dlundblad]

Originally Posted By: zeng
Operating viscosity of spec'ed mineral 80W90 (AGMA 4EP/ISO 150) is often higher than that of synthetics 75W90 (AGMA 3EP/ISO 100) at typical operating temperature .

Thus offering higher EHL film thickness and tipping towards EHL/Full film hydrodynamic lubrication away from Mixed/Boundary lubrication in a a typical differentials.


I've always read here they can be used interchangeably on most vehicles.

 

[zeng]

Originally Posted By: dlundblad
Originally Posted By: zeng
Operating viscosity of spec'ed mineral 80W90 (AGMA 4EP/ISO 150) is often higher than that of synthetics 75W90 (AGMA 3EP/ISO 100) at typical operating temperature .

Thus offering higher EHL film thickness and tipping towards EHL/Full film hydrodynamic lubrication away from Mixed/Boundary lubrication in a a typical differentials.


I've always read here they can be used interchangeably on most vehicles.



Only IF differential operating temperature is at 100*C , or thereabout.

But, they are Not.

Hence the myth.

 

[Yah-Tah-Hey]

Doesn't make any difference. Picking **** with the chickens.

 

[stchman]

Either gear oil will work.

 

[Greasymechtech]

Either will work fine. I prefer full synthetic which will usually be 75w90. Don't worry about AGMA ratings... common to the industrial equipment I work with at constant temp and speed indefinitely. AGMA is something I don't even consider when looking for a fluid for my vehicle gearboxes.

What differential and climate? 75w110 and 75w140 are tolerable by most differentials. And, thicker is a worthy attempt at band aiding under performing diffs with higher failure reputations.

 

[nyumski]

I dont have any clue about AGMA rating since in my manual, it doesnt tell anything. So the conclusion it is still okay using 75w90 rather than manual book says 80w90, right?
If it will maybe affect later in the future,im gonna back using 80w90 (before use mobillube hd 80w90)

 

[mongo161]

IMO.....Just use a 50/50 mix of Full Synthetic 75w90 and full synthetic 75w140.

That should bring you into the viscosity range of a conventional 80w90 with the benefit of synthetic.

 

[zeng]

Originally Posted By: mongo161
IMO.....Just use a 50/50 mix of Full Synthetic 75w90 and full synthetic 75w140.

That should bring you into the viscosity range of a conventional 80w90 with the benefit of synthetic.



That's it mongo161

.......... if one considers mineral oils as devils.