I always use OEM. Only bummer I saw this last time with Toyota was they only sell 50/50 premix, so I could not really "Flush" with a few gallons of Distilled water, then drain and fill with concentrated... Well, not thinking I actually did that, but could only get like 2 or so of 4 gallons per drain. So being paranoid about having too diluted of a mix I ended up doing 3 drain and fills with premix over the next 2 months...
Moving forward, I'm probably going to do a drain/fill every two years [pretty easy on a truck really] thus keeping it half fresh most of the time.