Viscosity index of ATFs

[threeputtpar]

I'm looking for a replacement ATF for my A6, and I've found Mystik Multi-Vehicle ATF at my local Fleet Farm for $4.16/quart. Here is the PDS.

Mystik ATF

I currently have Pentosin ATF1 in the trans, Pentosin ATF
and I am trying to figure out how the semi-synthetic Mystik can have a higher VI than the fully synthetic Pentosin. With all other stats the same, is the Mystik a better choice for service fill? Both meet the LT71141 that the Audi spec is based on.

Any thoughts?

 

[MolaKule]

Quote:
I am trying to figure out how the semi-synthetic Mystik can have a higher VI than the fully synthetic Pentosin.


Simple, they add more Viscosity Index Improver (VII) polymers.

They both have VII's in the formula.

 

[ledslinger]

Amsoil is 168.

 

[threeputtpar]

Yes, I looked into Amsoil ATF, but even the wholesale price I can get from my dealer friend is around $9/qt. I plan on changing it often enough that it wouldn't be cost effectivet to go with Amsoil, and plan on changing it even more often if I get the car chipped and am pushing the max HP and TQ the trans can handle.

I guess the question I really was asking is with the additional VIIs to get the VI up over 200, would that necessarily be a bad thing in a transmission? I realize that it would be bad in the heat of a twin turbo engine, but the trans rarely sees temps over 90 degrees C. Will the VIIs be a good thing for cold weather performance or a bad thing when/if they break down?

 

[MolaKule]

Quote:
Will the VIIs be a good thing for cold weather performance or a bad thing when/if they break down?



In general, it would help low temperature performance in cold weather.


Much depends on the base oil mix since most blenders tend to be using GroupIII as a correction fluid for "Blends."


ATF VII's are a different additive chemistry than those used in engine oils or gear lubes, and since they see no combustion gases, they do not break down as quickly as those in an engine.

I would favor the Pentosin ATF or Amsoil over the Mystic.

 

[threeputtpar]

Thanks for the help, MolaKule. I think when I dump the ATF1 in the spring I'll stop being so cheap and go with RL D4 which I can get for $8/qt at a local jobber shop. That should help with the shudder on the 2-3 upshift that prompted me to think of using a high VI fluid in the first place. VI of 198 and full synthetic, probably the best choice available.