In Reply to: Hydraulic Fluid - Dexron III equivalent posted by Paladin (Bob In PA) on January 03, 2011 at 14:09:19:
I agree with Jock - there is a big diffrence between the performance of ATF and AW hydraulic oils but any of them will work in this application. However I think AW 46 is closer to SAE 20 than SAE 10W and won't perform as well when cold. The viscosity of SAE 10W motor oil is anywhere in the range of 4.1-5.5 cSt@100C. Assuming a VI of 100 for a conventional mineral oil:
Viscosity of AW 32 = 5.6 cSt @100C (minimum for SAE 15W, SAE 20W and SAE 20)
Viscosity of AW 46 = 6.7 cSt @100C (still higher in the SAE 20/20W bands)
Dexron III on the other hand has a viscosity of 34 cSt @40C (ISO 32) and a VI of 180. That allows it to maintain a viscosity of 7.2 cST @100C (middle SAE 20).
So I'd go with the Dexron III or a similar universal tractor transmission fluid (UTF - bet you have buckets of that on hand). Because they have much higher VI's they perform better over a wider temperature range than AW oils. You will see a big improvement in cycle time when the oil in your splitter is still cold. That's a plus if you are like me and only split a couple days supply at a time.
TOH
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