Just a quick question. I'm not looking for people to say whether it's right or wrong to use engine oil as atf. This is more of a theoretical question as I have no intention of doing this, I just got to thinking. If you used engine oil would it act more like a non friction modified fluid such as type f or would it act like something highly friction modified such as atf+4 or dw1?
Using engine oil as atf
- Thread starter joegreen
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I'm going with friction modified. The only basis I have for that is how engine oil acts in shared sump motorcycles. Seems most of the time those clutches work just fine, although there are some reports of certain 'auto' oils causing some slippage.
More importantly, is how it acts in the hydraulic circuits. I'm betting that they are what really don't appreciate the viscosity of motor oils. You'd probably have all sorts of problems with apply times, etc.
More importantly, is how it acts in the hydraulic circuits. I'm betting that they are what really don't appreciate the viscosity of motor oils. You'd probably have all sorts of problems with apply times, etc.
It would depend on the additive packages. That's a question for resident chemist Molakule.
I lean towards type f... Motor oil is attempting to modify and or eliminate friction as much as possible.
Whereas say Dexron III is a fluid that modifies friction in a different way... Stick-slip. This fluid utilizes a coefficient of friction that best help the transmission function as desired by maintaining a balance between friction and proper friction management aka slippage.
Then a CVT fluid utilizes friction modifiers that help the oil maintain grip with a traction coefficient.
Whereas say Dexron III is a fluid that modifies friction in a different way... Stick-slip. This fluid utilizes a coefficient of friction that best help the transmission function as desired by maintaining a balance between friction and proper friction management aka slippage.
Then a CVT fluid utilizes friction modifiers that help the oil maintain grip with a traction coefficient.
Don’t original Humvees use engine oil as tranny fluid?
There are some engine oils that carry an Allison approval for off-highway use.
Check out this document from Red Line Oil. It mainly discusses manual transmission fluids, but there's a graph that reveals the coefficient of friction of several fluids. The graph shows that at most RPM, SAE 30 SF motor oil has a higher coefficient of friction than 80W GL-1, 80W GL-5, Dexron II ATF, and Red Line MTL. According to Red Line:
https://www.redlineoil.com/content/files/tech/MTL%20and%20MT-90%20Tech%20Info.pdf said:
I don't know...does motor oil coefficient of friction change much when moving up the chain of API categories?
The US military uses 15W40 MIL-L-2104 F and 0w20 MIL-PRF-46167 D engine oils in their Allison automatics for logistics commonality with the engines. Allisons are typically validated on this as part of the test program.
It depends on the vehicle. The British Mini and 1100 (the latter sold as the Austin America in the U.S.) used a 4-speed automatic transmission located in the engine sump that shared the engine's oil. Needless to say, engine combustion byproducts in the oil did the trans no good, and friction material plus metal filings from the trans did the engine no good, and letting the oil level fall (people in the U.S. were lax in checking) was disastrous - but that's another story.
I don't know of any other passenger car autoboxes that used straight engine oil but there may be others. The original 1940 GM-Oldsmobile Hydramatic used something called "GM Transmission Fluid No. 1" that was basically engine oil with a few additives to prevent excess wear and oxidation:
I don't know of any other passenger car autoboxes that used straight engine oil but there may be others. The original 1940 GM-Oldsmobile Hydramatic used something called "GM Transmission Fluid No. 1" that was basically engine oil with a few additives to prevent excess wear and oxidation:
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- Oct 10, 2020
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To answer why we don’t use conventional engine oil in trany is the video by uk omega fluids, which shows even synthetic oil churned up causes foaming n bubbles, while atf Adheres to moving gears without foaming. The new synthetic 0w40 motor oils might comeback close to ATF standards, someone will have to do YouTube test and see.
So the reverse is true we might use atf as engine oil due to hi temp tolerance. The enemy of tranys is not friction, but the resulting heat that is. It dissipated without a trany fluid radiator, which many new vehicles have. Many manufacturers like volvo, Toyota are putting three rads in sequence at front exactly for heat mitigation for both engine oil and radiator.
I like to talk about duralube, which started the entire synthetic motor oil industry when they came out in 1990s. And u won’t believe it seals gaskets n stops oil burning until u fix 10yr old plus cars burnin black smoke. What no one has tried is putting only duralube oil metal treatment only in trany, and I bet it would act much like Mobil, or royal purple synthetics ATFs. Judging by the cloudy sheen in most 5L gallon jug of synthetic oils sold in retail, there must be at least 500ml of duralube metal treatment in it.
Most of the advance synthetics won’t improve much more than today’s specs. The prospects of nano titanium, molebdynum, nano carbon piston Orings, or new electromagnetic piston induction, or molyebdium coated carbon-nano piston walls, that’s pretty much all folks. And Tesla’s new 400watt per kg nano copper batteries will demolish the oil and gas industry in next decade! Soon we’ll be upgrading petro engines with induction motors and batteries!
So the reverse is true we might use atf as engine oil due to hi temp tolerance. The enemy of tranys is not friction, but the resulting heat that is. It dissipated without a trany fluid radiator, which many new vehicles have. Many manufacturers like volvo, Toyota are putting three rads in sequence at front exactly for heat mitigation for both engine oil and radiator.
I like to talk about duralube, which started the entire synthetic motor oil industry when they came out in 1990s. And u won’t believe it seals gaskets n stops oil burning until u fix 10yr old plus cars burnin black smoke. What no one has tried is putting only duralube oil metal treatment only in trany, and I bet it would act much like Mobil, or royal purple synthetics ATFs. Judging by the cloudy sheen in most 5L gallon jug of synthetic oils sold in retail, there must be at least 500ml of duralube metal treatment in it.
Most of the advance synthetics won’t improve much more than today’s specs. The prospects of nano titanium, molebdynum, nano carbon piston Orings, or new electromagnetic piston induction, or molyebdium coated carbon-nano piston walls, that’s pretty much all folks. And Tesla’s new 400watt per kg nano copper batteries will demolish the oil and gas industry in next decade! Soon we’ll be upgrading petro engines with induction motors and batteries!
We didn't do anything special relative to this on our Allisons (planetary transmissions with disc clutches, much like automotive only larger in size) when we validated them for the US Army on mil spec engine oil - dino 15w40 as i detailed above. There are slightly higher spin losses due to viscosity compared to Dexron but durability was not an issue at all.
MolaKule
Staff member
Each fluid type and fluid application has a different additive package and contains different Friction Modifier Chemistry and AW chemistry for the specific materials used in Engines, transmissions, and differentials.
The friction modifiers in engine oils are NOT the same friction modifiers as found in ATF's. The friction modifiers in ATF's are NOT the same friction modifiers as found in LSD gear oil. The friction modifiers found in ATF's are NOT the same friction modifiers as found in Hy-Gard or UTTO fluid or a Trans-Hydraulic fluid. The friction modifiers found in Hy-Gard or UTTO fluid or a Trans-Hydraulic fluids are NOT the same friction modifiers found in ATF, etc. etc.
The friction modifiers in engine oils are NOT the same friction modifiers as found in ATF's. The friction modifiers in ATF's are NOT the same friction modifiers as found in LSD gear oil. The friction modifiers found in ATF's are NOT the same friction modifiers as found in Hy-Gard or UTTO fluid or a Trans-Hydraulic fluid. The friction modifiers found in Hy-Gard or UTTO fluid or a Trans-Hydraulic fluids are NOT the same friction modifiers found in ATF, etc. etc.
Yes, and each friction modifier, regardless of type, results in a dynamic coefficient of friction that can be objectively measured. Red Line points out, interestingly, that some motor oil has a higher coefficient of friction than even their MTL. ATF's are also depicted in the graph, so it's noteworthy here:
https://www.redlineoil.com/content/files/tech/MTL%20and%20MT-90%20Tech%20Info.pdf said:
In addition, in terms of dynamic coefficient of friction, some motor oils are suitable for manual transmissions, but nevertheless have problems with the static and low velocity coefficient of friction, thus making them unsuitable for this application.
https://www.redlineoil.com/content/files/tech/MTL%20and%20MT-90%20Tech%20Info.pdf said:
Some may find it surprising that motor oil has such a "high" coefficient of friction.
Read your article here: https://www.bobistheoilguy.com/forums/threads/atf-and-friction-modification.85480
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I did not judge or correct anyone's knowledge. I was agreeing with MolaKule about different oil types containing different friction modifiers. I was not instructing him to read his own article, which I linked, but rather indicated that I had done so. I used informal English in stating "Read your article here:," and I see now that the meaning was ambiguous. The word "read" is past tense, pronounced "rɛd," and the initial "I" was (informally) left out. Informative article, by the way.
I also referenced some research from Red Line Oil. In the following graph (sourced from the pdf quoted below), we can see that motor oil (top line, SAE 30 SF) generally has a higer coefficient of friction than Dexron II ATF (middle line). On the right side of the graph, we see the relationship change. Red Line indicates this:
https://www.redlineoil.com/content/files/tech/MTL%20and%20MT-90%20Tech%20Info.pdf said:
Today's gasoline oils (SM, SN, SP) are very slippery, Diesel oils less so Some diesel oils even meet the low end of the MA2 grip), and for those of us with automatic transmissions in our Mini's, the difference is clear. Moving to MA2 makes a huge difference in slippage and oil cleanliness from particles worn off by the slippage.
Although the discs are not bronze, they need to grab. Here is one of the clutch packs disassembled (damaged).
Although the discs are not bronze, they need to grab. Here is one of the clutch packs disassembled (damaged).
MolaKule
Staff member
While remotely interesting, I don't see how the Redline graph is material to the discussion of FM's in ATF's, especially as they relate to the wet clutch plates in AT's.
Each type of friction modifier (FM) has a different chemistry. There is a specific set of FM chemistries for engine oils, specific FM chemistries for ATF's, a different FM chemistry for LSD differentials, and different FM chemistries for other applications.
joegreen said:
It would not act like any of those and would be a bad idea, because an incorrect FM chemistry is being used to upset the required dynamic coefficient of friction for wet clutch plates.