Premium Conventional Rear Axle Lubricant Viscosity Blending - Any Additive Package Concerns?

[Apples]

Conventional oil (with little to no friction modifier/s added) recommended for my axle's recent EATON Detroit Truetrac installation, EATON's rec being 80W-90.

Installer used for a new ring-and-pinion break-in period a complete 2.75 qts fill using conventional 85W-140.

Liking the idea of 140 but not wanting to stray too far from EATON's standard recommendations, I am considering splitting the difference once the 500-mile break in period is complete and after a thorough axle drain then the installation of a diff cover giving an additional .75 qt capacity, using 2 qts Motorcraft SAE 80W-90 Premium Rear Axle Lubricant and 1.5 qts Mobilube HD Plus Gear Oil 85W-140. resulting in a +/- 82W-112 gear oil.

My concern is with any incompatibility of the two products' additive packages... While I would think this a non issue it seems wise to ask knowledgeable people first. Thanks for any reply.

 

[MolaKule]

Here is my suggestion:

Post in thread 'Nissan Frontier; question about differential lube choices'

Oct 2, 2024

@Rally2045 I would use a synthetic 75W110 because it has better both low and high temperature performance and thicker oil film.

• MolaKule

• 

 

[Apples]

Thank you for your reply!

Ah! Yes. I know it's out there, but it is a synthetic when I wish to stay with a conventional lubricant as per EATON's recommendations.

Thanks again.

 

[Apples]

One more time:

I suppose I have clouded the question here so I'll post it again.

Of the two lubricants linked in bold in my first post, are there any concerns w/ blending their respective additives? Or is this question unanswerable?

The question is not conventional vs. synthetic. These are conventional oils and I wish to blend them. Yay/nay?

Thanks again for any reply. Cheers.

 

[4WD]

It’s just a quess if those two mixed would perform well …
If I wanted a mid viscosity - Amsoil makes a 110 that’s properly formulated

 

[Apples]

Thanks 4WD for your reply.

Is that Amsoil product a conventional? or a synthetic... I'm looking to use a conventional oil.

I ask because I'm not finding an Amsoil 75W (or 80, 85) - 110 that is not a synthetic.

 

[4WD]

Thanks 4WD for your reply.

Is that Amsoil product a conventional? or a synthetic... I'm looking to use a conventional oil.

I ask because I'm not finding an Amsoil 75W (or 80, 85) - 110 that is not a synthetic.

It’s synthetic - that subject has been around along time and some ignore comments from Eaton …
Case in point is when Eaton states something - but AAM builds an axle for GM - and in the end GM has to decide what’s best for all components in the assembly …

If you want to stay conventional - two grades from the same company are a safer bet. I have done that with Valvoline white bottle gear lubes … (mix 90+140) …

 

[SubieRubyRoo]

One more time:

I suppose I have clouded the question here so I'll post it again.

Of the two lubricants linked in bold in my first post, are there any concerns w/ blending their respective additives? Or is this question unanswerable?

The question is not conventional vs. synthetic. These are conventional oils and I wish to blend them. Yay/nay?

Thanks again for any reply. Cheers.

Mixing fully-formulated lubes is generally frowned upon by oil blenders, as @MolaKule gave you a reference to. The winter rating does not “blend” and can only be as good as the worst fluid in the mix; in your case an 85W.

So, you’d have an 85w110 after mixing, which would arguably be worse in most if not all metrics compared to the idea of selecting a 75w110 as MolaKule proposed. It’s always safer and usually better overall to pick the best fluid with the correct viscosity, rather than playing backyard chemist and mixing different products that may not always react as expected. JM2C.

 

[Apples]

The winter rating does not “blend” and can only be as good as the worst fluid in the mix; in your case an 85W.

It’s always safer and usually better overall to pick the best fluid with the correct viscosity, rather than playing backyard chemist and mixing different products that may not always react as expected. JM2C.

Very good. This is exactly why I posted my question to begin with: to hear experienced replies.

And our good friend MK suggested I use a synth when it was previously stated here in this thread that a synth was not desired in this case (is synthetic desireable? YES. In just about everything else).

In the interest of preserving the Detroit Truetrac's designed torque bias ratio, and not altering that to any degree by using oils and/or additives (friction modifiers) not specifically suggested by EATON is my goal. Again, EATON has suggested a conventional oil for use with their Truetrac gear-type limited slip differential.

Yet I do not wish to run a -90, either. It looks like I will now simply stay with one product, that product already in stock here at my place, that being the Mobilube HD Plus Gear Oil 85W-140.

Thanks, everyone, for your help. Cheers.

 

[MolaKule]

Very good. This is exactly why I posted my question to begin with: to hear experienced replies.

And our good friend MK suggested I use a synth when it was previously stated here in this thread that a synth was not desired in this case (is synthetic desireable? YES. In just about everything else).

In the interest of preserving the Detroit Truetrac's designed torque bias ratio, and not altering that to any degree by using oils and/or additives (friction modifiers) not specifically suggested by EATON is my goal. Again, EATON has suggested a conventional oil for use with their Truetrac gear-type limited slip differential...

I know that's what Eaton suggests but in my Nissan Frontier Torsen-type LSD differential Nissan specifies either a synthetic 75W90 (with the automatic) or a 75W140 for the manual transmission version.

No Torsen-type differential should should have any additional LSD additive mixed into the lube because the Torsen-type differential has no plate or cone clutches.

 

[Apples]

I know that's what Eaton suggests but in my Nissan Frontier...

No Torsen-type differential should should have any additional LSD additive mixed into the lube because the Torsen-type differential has no plate or cone clutches.

Well, that's pretty obvious. I am very familiar with how a helical gear-type LS works and the sheer simplicity of the aggregate components.

I had simply asked here about blending additive packages, and it has been determined that that's not great idea. Point taken.

That had answered my question.

I posted the following in another thread so I'm repeating it here:

"I actually called EATON and spoke to the man who picked up the Detroit Truetrac tech line... to ask him directly about their Owners Manual-published rec of 80W-90, that I had been looking specifically for a lube with no added friction modifiers, etc... and that my installer for the new ring-and-pinion used an 85W-140...

To which he replied in so many words, "the difference in the -90 and the -140 as to the torque bias ratio being dependent on designed internal friction of the unit, you more than likely will not be able to notice. Carry on." And as to the amount of lubes on the shelf today that have added friction modifiers he said the same thing: That I would not be able to notice. He said of course we do not wish to add any on top of that. I mentioned I would be using a lube distinctly devoid of any FMs as per EATON's published recs but with the slight variation on lube viscosity.

As to the use of synthetic axle lube for the Truetrac, he mentioned that there had not been enough testing done by EATON for them to recommend it's use, first of all, and secondly, the change in internal friction may be so much that the unit's torque bias *may* be altered to the point of diminished performance (although with no harm to the unit itself)."


We all have our comfort zones. Mine is trying my best to stay with EATON's recommendations until I think I might know better. The quest for a greater viscosity than dash90 stems from the experience of users of Ford products and the experience of axle/differential installers' recommendations of a dash140 where I was only trying to split the difference while staying with a conventional lube. End of story.

 

[MolaKule]

My concern is with any incompatibility of the two products' additive packages... While I would think this a non issue it seems wise to ask knowledgeable people first. Thanks for any reply.

I see no problems in the additive chemistry. I change the run-in lube within 500 miles.

 

[wlk]

80w90 has done just fine in my c1500 for >30k miles. I have towed our 27ft camper with it for 4 yrs now and no concerns. Run what you want but there is nothing wrong with running 80w90.

 

[barkingspider]

I had a frankenbrew of different brands 80w90, 75w90 and 140 in the rear diff of GM trucks I owned in the past. They all ran fine, no issues, no noise. Not saying it’s best but i think you’ll be fine if you mix.

 

[Apples]

Update - and thanks again to those who've replied.

Looking back, I had acquired 490 miles by about November 4th, prepped my PML finned aluminum diff cover (w/ included stainless hardware!) for the break-in drain, interior diff housing wipe clean, cover flange clean and prep for cover, using Permatex's Gear Oil silicone gasket maker.

That product's directions suggest application, apply cover, finger-tighten cover bolts, wait one hour, then torque cover bolts (90 ft/lb), THEN wait another! 24 hours before adding diff lubricant. Had I needed to drive the truck sooner obviously I would hired a ride.

I follered the Permatex directions, there are no leaks, this after 5+ weeks of regular driving and have installed 3 qts of Motorcraft 80W-90 Premium Rear Axle Lubricant using no extras.

Truck runs strong, axle noise nonexistent, the 4.09 gearing on the money for the 6R80 transmission and for this 34" tire. Really happy w/ this gear change. Thanks again. Cheers!

 

[D1dad]

I don’t know who makes motorcraft “premium lube” but I’ve used oem, amsoil, motul and have some schaffers going in this spring in our awd 18 rogue. Motul up till now has produced the best results.

 

[Randy_R]

I would stay with mfg. recommended. I don’t see any benefit from anything but that. I run 80W-90 in old school 12 bolt Positraction because that is what the manual recommends. Currently Valvoline conventional with GM additive. Castrol and Penn Grade 1 have additive already in it.

 

[SubieRubyRoo]

Conventional oil (with little to no friction modifier/s added) recommended for my axle's recent EATON Detroit Truetrac installation, EATON's rec being 80W-90.

Installer used for a new ring-and-pinion break-in period a complete 2.75 qts fill using conventional 85W-140.

Liking the idea of 140 but not wanting to stray too far from EATON's standard recommendations, I am considering splitting the difference once the 500-mile break in period is complete and after a thorough axle drain then the installation of a diff cover giving an additional .75 qt capacity, using 2 qts Motorcraft SAE 80W-90 Premium Rear Axle Lubricant and 1.5 qts Mobilube HD Plus Gear Oil 85W-140. resulting in a +/- 82W-112 gear oil.

My concern is with any incompatibility of the two products' additive packages... While I would think this a non issue it seems wise to ask knowledgeable people first. Thanks for any reply.

Well it seems like you’ve got some misconceptions about mixing different oils. Since mixing different viscosities doesn’t “average out” with respect to grades (you can’t end up in between the established numbers), let’s review your 80w90 + 85w140: winter grades must always default to the worst rated, so your overall mixture is going to be an 85W. Now, a 90 grade gear oil + 140 grade, since there is no “112” grade, means your result there would still be classified as a 140 grade.

In other words, after going through the ordeal of buying two different oils and mixing them to come up with unknown chemistry and not knowing if the resultant mixture is compatible, you’ve ended up with a slightly thinner fluid at operating temperature that has the worse cold characteristics of the two. Seems like an exercise in futility, eh?

Just pick one or the other, no mixing. Since you’re so concerned with following Eaton’s recommendations, do they recommend a fluid, and if so, why not use that?

 

[Apples]

I don’t know who makes motorcraft “premium lube” but I’ve used oem, amsoil, motul and have some schaffers going in this spring in our awd 18 rogue. Motul up till now has produced the best results.

That's how Motorcraft has chosen to label the bottle. It is not my description.

Well it seems like you’ve got some misconceptions about mixing different oils. Since mixing different viscosities doesn’t “average out” with respect to grades (you can’t end up in between the established numbers), let’s review your 80w90 + 85w140: winter grades must always default to the worst rated, so your overall mixture is going to be an 85W. Now, a 90 grade gear oil + 140 grade, since there is no “112” grade, means your result there would still be classified as a 140 grade.

In other words, after going through the ordeal of buying two different oils and mixing them to come up with unknown chemistry and not knowing if the resultant mixture is compatible, you’ve ended up with a slightly thinner fluid at operating temperature that has the worse cold characteristics of the two. Seems like an exercise in futility, eh?

Just pick one or the other, no mixing. Since you’re so concerned with following Eaton’s recommendations, do they recommend a fluid, and if so, why not use that?

Thanks for your two cents! sir. Apparently, you didn't catch the posted update a little farther down in the thread, or where the issue of blending winter grades was resolved. And, one can indeed "blend" viscosities (although not the components that create the Winter rating?). It's true. That, from an SAE motor oil engineer himself. I'll dig up the name and the book.

As for the ordeal of buying two different oils and mixing... that's not how it played out. If you had read the thread you'd have perhaps been aware that the gear set installer used an 85W-140 for the break-in period. I already had both the Mobil HD 80W-140 conventional the Motorcraft Premium (conventional) 80W-90 in stock, the 80W-90 per EATON's recommendations for after 500 mile break-in.

Ford had spec'd 140 for use in earlier 8.8 axles - and - since the installer had used the 85W-140 I started warming up to the idea and then WONDERED if mixing the two (85W-140 and 80W-90) were a THING and IF SO, then... best of both worlds.

However, by the time 2016 rolled around Ford perhaps wanting to add to their CAFE numbers and/or through development testing, etc, had found the 80W-90 sufficient, as had EATON a 80W-90 conventional oil for their own product.

Either way, again, as has been posted earlier in this thread, I had become better informed thanks to BITOG contributors like yourself and the decision was made to stick w/ the Motorcraft 80W-90 Premium Rear Axle Lubricant which now resides in the axle and I couldn't be happier.


Cheers.

 

[SubieRubyRoo]

That's how Motorcraft has chosen to label the bottle. It is not my description.






Thanks for your two cents! sir. Apparently, you didn't catch the posted update a little farther down in the thread, or where the issue of blending winter grades was resolved. And, one can indeed "blend" viscosities (although not the components that create the Winter rating?). It's true. That, from an SAE motor oil engineer himself. I'll dig up the name and the book.

As for the ordeal of buying two different oils and mixing... that's not how it played out. If you had read the thread you'd have perhaps been aware that the gear set installer used an 85W-140 for the break-in period. I already had both the Mobil HD 80W-140 conventional the Motorcraft Premium (conventional) 80W-90 in stock, the 80W-90 per EATON's recommendations for after 500 mile break-in.

Ford had spec'd 140 for use in earlier 8.8 axles - and - since the installer had used the 85W-140 I started warming up to the idea and then WONDERED if mixing the two (85W-140 and 80W-90) were a THING and IF SO, then... best of both worlds.

However, by the time 2016 rolled around Ford perhaps wanting to add to their CAFE numbers and/or through development testing, etc, had found the 80W-90 sufficient, as had EATON a 80W-90 conventional oil for their own product.

Either way, again, as has been posted earlier in this thread, I had become better informed thanks to BITOG contributors like yourself and the decision was made to stick w/ the Motorcraft 80W-90 Premium Rear Axle Lubricant which now resides in the axle and I couldn't be happier.


Cheers.

You ended up choosing wisely, but you missed my point; maybe my bad on not explaining well enough. You can certainly mix viscosities, but one cannot arbitrarily create grades (112 grade). The final product will always fall into an existing grade and must be considered as such. Since your proposed mix was a 112, and there is no 112, it must fall into the next higher choice. In gear oils, since it is above a 110 grade, that means it must still be called a 140 grade, albeit on the very thin side for it.

It’s always safer, as you chose, to stick to a single fluid choice. You simply have to pick the best compromise of all attributes for your goals.