Mixing Fluids Caues Foaming? Anything Else?

[viscous]

Mixing automotive fluids is generally neither necessary nor recommended. However, people do mix fluids for various reasons, and I'm curious about possible unexpected results, such as precipitation and foaming. Here are some examples:

I mixed [hydraulic fluid and ATF] in our lift at work and it foamed.

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

Automotive fluids (motor oil, gear oil, atf, hydraulic oil, etc.) consist of base oil, an additive package, and possibly viscosity index improver. Additive packages are carefully formulated, as individual additive compounds may interact synergistically or antagonistically, and may even function differently depending on the base stock. Mixing automotive fluids of different types produces an oil of unknown viscosity and performance properties. Presumably, the base oils would mix amicably (right?), but "mixed" additives would offer different levels of protection and the "mixed" VIIs would function differently than intended.

However, what would cause a mixture oil to exhibit odd behavior such as foaming? Has anyone actually observed this result? Is additive precipitation another possible outcome? What else can happen (besides altering the fluid's effectiveness)?

 

[ABN_CBT_ENGR]

Personally I observe it all the time with industrial lubricants and a lube tech just grabbing the first jug he gets and not caring about the color band and markings.

The question as phrased is literally too broad to be effectively addressed because depending on the products mixed and the volumes mixed and process factors such as tramp chemicals, heat, mechanical forces ( kinda like a heated blender)

You can literally get just about anything as a result from a chocolate brownie to an explosion or combustion.

I have has many OA's come back with stiff warnings on "what is this you sent us?" based on what its supposed to be.

 

[viscous]

The question as phrased is literally too broad to be effectively addressed because depending on the products mixed and the volumes mixed and process factors such as tramp chemicals, heat, mechanical forces ( kinda like a heated blender)

As I have mentioned in another thread, I'm considering topping off manual transmission fluid (low viscosity GL-4 gear oil) with 5-10% motor oil or universal tractor hydraulic fluid. Any thoughts on that?

 

[ABN_CBT_ENGR]

As I have mentioned in another thread, I'm considering topping off manual transmission fluid (low viscosity GL-4 gear oil) with 5-10% motor oil or universal tractor hydraulic fluid. Any thoughts on that?

Unfortunately, I am on the ME side of tribology and not a qualified chemical engineer, chemist or lab rat so for any specifics you should defer those questions to those here who are.

In my experience I have seen gear oils cut with hydraulic fluid (never motor oil) and anecdotally it skewed the OA so it never stayed in long enough to do damage ( in many cases in industry, when an OA flags something, a change is routinely scheduled PDQ then an evaluation)

Plus we use other PdM technologies in conjunction.

 

[viscous]

Unfortunately, I am on the ME side of tribology and not a qualified chemical engineer, chemist or lab rat so for any specifics you should defer those questions to those here who are.

Thanks for your info, nevertheless.

 

[MolaKule]

As I have mentioned in another thread, I'm considering topping off manual transmission fluid (low viscosity GL-4 gear oil) with 5-10% motor oil or universal tractor hydraulic fluid. Any thoughts on that?

Foaming and precipitation (not defined) are NOT the issues.

You continue to ask the same question and have been given informed responses but here is a summary:

The responses were that it is not a good idea to mix the fluids because:

1. Dilution of the Anti-Wear chemistry,

2. Dilution of the Friction Modifier chemistry,

3. Resulting viscosity may not provide sufficient film strength,

4. Dedicated, finished and formulated MTF's with the proper additive chemistry and base oil mix are available today so why take a chance on mixing your own with the resulting fluid not being what is needed?

 

[viscous]

Foaming and precipitation (not defined) are NOT the issues.

Precipitation refers to a dissolved solid becoming "undesolved."

You continue to ask the same question and have been given informed responses but here is a summary:

This thread was intended as a general inquiry about possible results from mixing fluids. ABN_CBT_ENGR mentioned that the question was quite broad, so I decided to reference my prior question.

The responses were that it is not a good idea to mix the fluids because:
1. Dilution of the Anti-Wear chemistry,
2. Dilution of the Friction Modifier chemistry,
3. Resulting viscosity may not provide sufficient film strength,
4. Dedicated, finished and formulated MTF's with the proper additive chemistry and base oil mix are available today so why take a chance on mixing your own with the resulting fluid not being what is needed?

Yes, I began this thread by indicating that mixing is not recommended. These are all good points, some of which I tried to address preemptively in my original post. Nevertheless, I find it interesting to learn about the effects of mixing fluids. I assume that you, as a chemist, find mixing interesting too, no? I do appreciate your advice, so thank you for your input.

 

[reddevil]

As I have mentioned in another thread, I'm considering topping off manual transmission fluid (low viscosity GL-4 gear oil) with 5-10% motor oil or universal tractor hydraulic fluid. Any thoughts on that?

Many years ago I bought my first car - manual NIssan Datsun 130Y. I had a "quak" mechanic servicing my car. The manual transmission seemed noisy. He recommended a concoction - replacing it with motor oil plus additive (not sure what it was). Anyway, the transmission seems to work ok, not as noisy and smooth - for about a month. Then one day on a shopping parking lot, the gear won't engage after starting the car!
I panicked not knowing what had happen. Fortunately after trying various gears, it engaged again.
I cannot remember if I replaced the fluid after that since it happened after a month after gear oil change and I didn't think it was related, but that was the one and only time. Sold the car a year later.
Gear oil and motor oil definitely don't mix.
My current 2L Nissan Qashqai (2015) is silent. If I am sitting inside the car at idle without radio/AC on at a traffic light, I would not know the car has started as there is no sound from engine, transmission or vibration from the steering wheel. It is not a start stop engine. Transmission and engine has come a long way and so has the fluid. Use fluid that is formulated for it.

 

[PimTac]

“Precipitation refers to a dissolved solid becoming "undesolved."


That’s not the way I understand precipitation. Usually incompatible components react and fall out in a solid or other visible manner.

 

[viscous]

Use fluid that is formulated for it.

Yes, motor oil plus mystery additive would be subpar. I was curious about the effect of a motor oil top-off. Here's an example:

I decided that instead of straight (synthetic) motor oil, 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.

However, this thread was actually intended to discuss mixing more generally.

 

[viscous]

“Precipitation refers to a dissolved solid becoming "undesolved."
That’s not the way I understand precipitation. Usually incompatible components react and fall out in a solid or other visible manner.

Yes, and dissolved substances can become undissolved:

The precipitation may occur if concentration of a compound exceeds its solubility (such as when mixing solvents or changing their temperature). Precipitation may also occur rapidly from a supersaturated solution.

 

[MolaKule]

... However, this thread was actually intended to discuss mixing more generally...

I still fail to see your point from the link in the above post or from your original post..

I know of no blender or formulator who would prepare such a solution for automotive applications that would be supersaturated in the beginning or become supersaturated in use.

And with that this thread has run its course.