ATF question

[aldive]

Does ATF, either synthetic or dino, loose its heat carrying ability as it ages?

 

[MONMIX]

I think so

 

[dogfriend]

This is an interesting question.

All materials have an inherent thermal conductivity which is a measure of how the material transfers energy (heat) per unit time. This rate depends upon the distance and type of bonding between molecules; solids conduct better than liquids, liquid conduct better than gases, metals conduct better than nonmetals.

So ATF should have an inherent thermal conductivity in its 'pure' state, but as the
ATF "ages" it will be contaminated by other materials (pieces of metal, fibers from bands, etc) . In material science terms, it will become a composite of ATF and the other contaminants in the mix. The thermal conductivity of the mix will become a composite of the various components. If the contaminants have better thermal conductivity than the ATF, it is possible that the thermal conductivity could get better. Its also possible(likely) that it could get worse, depending upon the composition of the band material. The effect wont be very significant one way or the other, because the contamination will be a small percentage of the volume of the fluid.

Even if the conductivity is slightly better, this is not a good reason to continue using contaminated ATF because the contaminates will tend to separate out and form a sludge between the ATF and the walls of the transmission. The sludge will prevent contact between the ATF and the aluminum case which may inhibit heat transfer between the ATF and the case.(Not to mention the potential for clogging valves and passages)If you want maximum heat transfer between the liquid ATF and the case then you want the ATF to "wet" the surface of the case which will carry the heat away.

Clean ATF is better than dirty ATF even if the contamination has high thermal conductivity.

 

[aldive]

After a tranny fluid flush ( complete ) last night, my tranny temp has dropped 20 F and the shifts are much better too.

 

[dogfriend]

Same type of ATF?

Did you see much difference in the color from old to new? I know youre using an external filter; I would think that your old ATF would still be in good shape.

 

[aldive]

Yes, same ATF, Mobil 1.