So I was at my local autozone picking up a quart of Mercon v for top off from my recent pan drop on my ranger and there was an older lady buying Castrol Edge 5w20 and an stp filter in line in front of me. The lady wasn't sure what oil went in her car and the guy behind the register told her that full synthetic was the way to go, but she "could not go back to conventional whatsoever once she started using the full synthetic". She asked him why and he didn't respond as it seemed that he was pretending to be involved in generating her order rather than giving an explanation which I too, was patiently awaiting his response on. Never came. I figure they are trying to push out some full syn inventory and that type of lady was the prime candidate.