MTF Top-off: PCMO or UTHF?

[viscous]

I'd like to top off some GL-4 manual transmission fluid with either (1) synthetic 10W-30 motor oil or (2) universal tractor hydraulic fluid. The top-off will constitute 5-10% of the total fluid volume. No synchronizers, so I'm not not too concerned about mixing the different friction modifiers of each fluid.

1. Is anyone aware of incompatibility issues associated with the proposed blends (e.g. foaming, precipitation, etc.)?
2. Would the 5-10% dilution severely reduce the GL-4 protection of the manual transmission fluid, or would the protection reduction be negligible?
3. Which fluid is best suited for this top-off, PCMO or UTHF? In terms of additive packge, I believe UTHF is a better match. I might prefer 10W-30, however, as it's a better viscosity match.

Here are some success and failure stories about mixing mtf/gear oil with PCMO.

I'd mix a quart of HMC's MTF (part no.08798-9031, white cap) with a quart of Mobil 1 10W-30. I can report that after approximately one year and 6K miles in an '02 Honda Si with 26K miles on the odometer, this nutty concoction seems not just adequate or "good" but great.

if you mix gear oil with motor oil ..you'll get spontanious foaming.

 

[Astro14]

Why not MTF?

 

[MolaKule]

What is type, brand or application for this transmission? What viscosity does this transmission require?

Different lubricants have different additives packages that may not be compatible.

 

[zeng]

I wouldn't give any undue consideration to PCMO , though more shear stable HDEO is acceptable if one is adamant in an engine oil .

My hunch is UTHF is preferred for its better and more appropriate additive package and stronger(?) shear stability for transmission use .

John Deere JD20C or Allison TES 353 approvals UTHF comes into mind , synthetic or mineral version .

TES 439 off-road approved oils in 15W40 may be considered for enhance component protection with thicker oil film thickness/strength . These TES 439's are typically HDEO (never an PCMO) oils complying with Allison additional performance requirements .

Edit : Caterpillar TO4 approved oils in SAE 30 may be another option for consideration , bearing in mind ambient temperature and shift .

 

[MolaKule]

I wouldn't give any undue consideration to PCMO , though more shear stable HDEO is acceptable if one is adamant in an engine oil...

...My hunch is UTHF is preferred for its better and more appropriate additive package and stronger(?) shear stability for transmission use .

UTHF does NOT have the proper MTF additive package.

Again, fluids of similar viscosity does not mean they have the proper additive packages for the specific application.

 

[viscous]

Why not MTF?

I'd like to use something that I have on hand.

What is type, brand or application for this transmission? What viscosity does this transmission require?

Application is a transaxle under light load where GL-4 is sufficient. Required viscosity is that of a typical UTHF or 20 grade motor oil, but the only THF I have on hand is of lower viscosity. Therefore, I'm considering topping with 10W-30 PCMO so as not to reduce the overall viscosity. Could top off with the thin THF if that would be better.

Different lubricants have different additives packages that may not be compatible.

What exactly does "incompatible" mean? If it means that different additives would be competing for finite space on the gear surfaces, would the proposed dilution (5-10%) be small enough to ignore this effect? Or does "incompatible" mean something more serious, such as the entire additive package could be "neutralized" or rendered ineffective? If diluting GL-4 MTF with 5% UTHF or PCMO means that the final blend would be 95% as effective as pure MTF, perhaps I could live with that.

UTHF does NOT have the proper MTF additive package.

I'd like to know more. What is it missing? I'm aware that there would be different friction modifiers, but I don't believe that's critical in my application, unless mixing the FMs could produce higher gear friction than produced using either fluid alone. Some UTHF blenders brag about their fluid's ability to resist wear, so I assume that ability may be on par with most GL-4 MTFs.

 

[MolaKule]

I'd like to use something that I have on hand...

...I'd like to know more. What is it missing? I'm aware that there would be different friction modifiers, but I don't believe that's critical in my application, unless mixing the FMs could produce higher gear friction than produced using either fluid alone. Some UTHF blenders brag about their fluid's ability to resist wear, so I assume that ability may be on par with most GL-4 MTFs.

You may want to study this info:

 

[viscous]

You may want to study this info:

Thank you. I had read your prior version of this in the Synchromesh thread, but it's nice to have a PDF. I'd be curious to know your thoughts the additive "compatibility" question I raised in post #6 above:

What exactly does "incompatible" mean? If it means that different additives would be competing for finite space on the gear surfaces, would the proposed dilution (5-10%) be small enough to ignore this effect? Or does "incompatible" mean something more serious, such as the entire additive package could be "neutralized" or rendered ineffective? If diluting GL-4 MTF with 5% UTHF or PCMO means that the final blend would be 95% as effective as pure MTF, perhaps I could live with that.

Would it be more "compatible" to add some Non-Detergent SAE 30W Lubricating Oil to the MTF? I can't imagine it would be any better to top off MTF with synthetic gear oil, but I've seen that referenced as well:

I found on another message board where people were mixing Pennzoil/GM synchromesh with regular 75w-90 gear oil with awesome results. I have to agree!

I realize this screws up the friction modification, but is that still a concern when synchronizers aren't involved?

 

[Lubener]

Use the correct stuff. I don't understand your reasoning of such a simple task.

 

[viscous]

Use the correct stuff. I don't understand your reasoning of such a simple task.

It would be convenient to use something I have on hand. I'd also like to learn a bit about additive compatibility in the process. I would agree that mixing fluids is generally not ideal.

 

[zeng]

Thank you. I had read your prior version of this in the Synchromesh thread, but it's nice to have a PDF. I'd be curious to know your thoughts the additive "compatibility" question I raised in post #6 above:

Would it be more "compatible" to add some Non-Detergent SAE 30W Lubricating Oil to the MTF? I can't imagine it would be any better to top off MTF with synthetic gear oil, but I've seen that referenced as well:

I realize this screws up the friction modification, but is that still a concern when synchronizers aren't involved?

I too am keen to learn what 'incompatible' mean specifically ....................
and , specific good/bad consequences of significance from OP proceeding with proposed 'incompatibility' regardless .

 

[viscous]

I too am keen to learn what 'incompatible' mean specifically ....................
and , specific good/bad consequences of significance from OP proceeding with proposed 'incompatibility' regardless .

Well, if I try it I'll keep you posted, ha ha. Just trying to learn some oil chemistry. I think we're all aware that mixing isn't ideal, but yet many folks here mix engine oils with glee. Of course, they're designed to be miscible.

 

[Astro14]

Seems like a lot of work, and some risk, to avoid buying another, what, quart of MTF?

 

[viscous]

Seems like a lot of work, and some risk, to avoid buying another, what, quart of MTF?

Perhaps, but maybe we can learn something about miscibility. Generally speaking, it's not a good idea to mix various types of fluids due to friction modifiers:

A IC engine's FM does not equal an ATF FM does not equal a Gear Lube FM nor does it equal the FM in a UTF. Different chemistries folks.

I believe it may be OK in certain situations, however. Perhaps MolaKule or others can offer further insight.

 

[kschachn]

Perhaps, but maybe we can learn something about miscibility. Generally speaking, it's not a good idea to mix various types of fluids due to friction modifiers:

What link is there between miscibility and the presence or absence of a friction modifier?

 

[viscous]

What link is there between miscibility and the presence or absence of a friction modifier?

Certain fluids, such as MTFs for synchronized transmissions, require a friction modifier that dynamically changes the coefficient of friction during operation. If you mix in a fluid that has a different friction modifier, say a GL-5 gear oil, the foreign friction modifier may screw up the MTF's intended friction properties:

The friction modifiers in the mtf fluids are going to be pre-empted by the fm's in the differential lubes. I recommend against this practice for mt's. For differentials, mix differential fluids only and break a leg.

In my application, I don't believe proper friction modification is critical. That's why I'm contemplating mixing. My main concern may be foaming, but I'm not sure if that's a realistic possibility.

 

[zeng]

It would be convenient to use something I have on hand. I'd also like to learn a bit about additive compatibility in the process. I would agree that mixing fluids is generally not ideal.

Some of us can understand and accept this practice of being convenient ......
and in this context I would abandon the 'oil company protocols' suggested by me earlier on and mix away PCMO 10W30/UHF available at hand and call it a day .

In my application, I don't believe proper friction modification is critical. That's why I'm contemplating mixing. My main concern may be foaming, but I'm not sure if that's a realistic possibility.

Potential foaming from the intended mixing and ratio ???
I would ignore its occurence potential as long as (mixed) oil fill level is adequate .

 

[kschachn]

Certain fluids, such as MTFs for synchronized transmissions, require a friction modifier that dynamically changes the coefficient of friction during operation. If you mix in a fluid that has a different friction modifier, say a GL-5 gear oil, the foreign friction modifier may screw up the MTF's intended friction properties:

Okay sure but that isn't miscibility.

 

[MolaKule]

Certain fluids, such as MTFs for synchronized transmissions, require a friction modifier that dynamically changes the coefficient of friction during operation. If you mix in a fluid that has a different friction modifier, say a GL-5 gear oil, the foreign friction modifier may screw up the MTF's intended friction properties.

I am not sure you have fully grasped the differences in friction modifiers. For an LS differential with flat plate or cone clutches that friction modifier is used to prevent chatter. In MTF's, the friction modifier is used to enhance synchro engagement/disengagement. The two chemistries are entirely different and react differently.

In my application, I don't believe proper friction modification is critical. That's why I'm contemplating mixing. My main concern may be foaming, but I'm not sure if that's a realistic possibility.

My main concern would be in the dilution of the MTF's anti-wear agents by the THF.

So what transaxle is this that has no need for a friction modifier? Is this an outdoor equipment transaxle?

 

[MolaKule]

Some of us can understand and accept this practice of being convenient ......
and in this context I would abandon the 'oil company protocols' suggested by me earlier on and mix away PCMO 10W30/UHF available at hand and call it a day.

And some of us actually understand the mechanics of transmissions and the need for proper fluid chemistry.