My uncle told me to use ATF to free a seized turbo actuator, and it worked.
I was working on a 2012 Duramax with a stuck VGT actuator, the kind that just won't budge. My uncle, who ran a fleet shop for twenty years, told me to forget the expensive penetrants and just drip a little automatic transmission fluid down the actuator rod. I was sure it would gum things up worse, but I tried it. I let it sit overnight, and the next morning, with some gentle heat from a heat gun, it broke free with almost no force. It saved me from pulling the whole turbo assembly. I've used it twice since on similar jobs. Has anyone else found a simple fluid that works better than the store-bought stuff for this kind of thing?