ATF Lacks Cleaning Detergents

Z15 said:

Dexron VI IS NOT a pao synthetic. Its what is referred to as a Group III base stock, PAO is Group IV

Nothing GM branded is PAO.

Click to expand...

Yes, I was thinking of the LV-ATF version, aka HP. The spec for it is simply titled Low Viscosity ATF https://standards.globalspec.com/std/13112609/GMW16954

The kinematic viscosity specs are the same as Dexron VI, but the LV (aka HP) reduces the Brookfield at -40 from 15,000 to 8,000.



Looking at the chart here, I think you can see why the spec was only able to be met by including some PAO when the spec first came out. I believe that GM revised the spec so that the much cheaper Group III could be used. I'm still pretty sure that it was actually Group 4 based fluid, when the LV (GM HP-ATF) was first introduced.

There are still plenty of GM licensed (branded) ATF today that include PAO. GM doesn't actually produce the ATF, they just license others to make it, and unlike companies like ZF, which typically only licenses one manufacturer at a time for a specific fluid, GM will allow more than one.

Regardless of what is actually licensed in a particular bottle, I still argue that it is pretty difficult to make a 6 cSt ATF (which is what both VI and LV-HP are spec'd at) which doesn't shear below 5.5 cSt in a 6000 lb truck/suv during the 100K mile life, without blending a lot of PAO.

@MWD_CTSV
100k miles? No sir, not me. I drive conservatively (no towing and/or hot rodding, no stop-n-go) and the Dexron6 in my Denali 6L80e was at 5.6 cSt with only 43k miles on the fluid. All 11-12 qts had been changed w/ACDeco Dexron6 pt# 10-9244, GM# 88865618, because I had the tranny out to change the engine rear main seal, Put in a new torque converter then for preventative mx.
Here the thread I did with a pic of my last 2 used atf reports:
https://www.tahoeyukonforum.com/threads/atf-lab-results-dexron-vi-43k-miles-on-fluid.134360/
Here's the thread I did w/pics when I changed torque converter:
https://www.tahoeyukonforum.com/thr...7-yukon-denali-6-2.108334/page-3#post-1293118

Thanks @donjetman ! Your reports are great! Your results with conservative driving matches the other evidence pointing to Dexron6 being more of a 50K fluid than 100K as GM says.

Even though GM doesn't call out a min viscosity for the fluid itself, it is included in the durability testing that 5.5 is the minimum. Since they state that the fluid life is 100K, I hold their feet to the fire so to speak that they are saying the fluid must still be in spec at that mileage, for at least the majority of vehicles.

Personally, I think licensed Dexron6 is a good fluid for our 6L80s, and I would rather use it and change it every 50K, than to spend double or more on a higher quality Group4 base fluid to get 100K.

To stay relevant to the detergents (additives) in ATF thread, I recommend using only licensed Dexron6, because GM is pretty rigorous about testing and the percentages in the blend. The additives are generally good enough to perform well (mainly meaning shift and anti-shudder) at lower percentages in the blend, even as low as 50% of the recommended amount, so you may be getting much less detergent/dispersant and the fluid life will be shorter, and you will get a lot more varnish deposits.

This stuff's been my favorite ATF for well over 10 years:

Vastly prefer changing the ATF and filter every 50,000miles.
However, if the transmission begins misbehaving, I'll change the ATF and filter ASAP.