Originally Posted by y_p_w
But of course the fluid change that has the smallest proportion of fluid removed is almost always an automatic transmission. You'd be lucky to get 40% out of there. Yet people change fluids, have no idea what the factory fill is, and sleep well at night.
Congratulations...you have won the strawman of the year award so far for 2019.
Firstly, this is a discussion regarding the mixing and compatibility of...engine oil...in an engine oil forum, discussing...engine oil.
Secondly, ASTM D6922 is described...by the ASTM as
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Standard Test Method for Determination of Homogeneity and Miscibility in Automotive Engine Oils
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1. Scope
1.1 This test method covers the determination if an automotive engine oil is homogeneous and will remain so, and if it is miscible with certain standard reference oils after being submitted to a prescribed cycle of temperature changes. This test method is very similar to the homogeneity and miscibility test described in FED-STD-791/3470.1.
So it takes an engine oil, mixes it with 7 reference oils, heats it and cools it and they are not allowed to split or blow chinks...that's it.
I've got the standard, and it in no way suggests that two or more ATFs, unrelated to any engine oil, being mixed in a tranny, of ill determined type specification in any way infers any compatibility or miscibility of completely unrelated fluids in completely unrelated compartments (engines).
The fact that you can mix Vodka and Orange juice, in any proportion and help you sleep at night is only marginally less relevant.