Simply because I see synthetic blends of motor oils everywhere I had believed that it was fine to mix the two when their specs were in order, but today the guy behind the counter at auto parts store #1 told me never to do that, since the two were immiscible. He likened them to oil and water. We were talking about ATF, so maybe there was something I was missing there. The guy at store #2 said not to worry.

And over at Valvoline they have on their FAQ saying that it's OK to mix synthetic ATF with dino (question 5: http://www.valvoline.com/faqs/system-fluids/automatic-transmission-fluid/). I'm inclined to believe they are OK to mix but searching has netted a lot of rote controversy. I just had to ask before I top off with Typpe F instead of the ATF +4 that's in there already. :) thanks fellas