One factor to consider, is 0w20 is only available as a synthetic oil, from any manufacturer. So if you're going to start messing with different grades, at least stick to full synthetic oils.
When we bought our 5th gen it was used, and the used car dealer had changed the oil as part of their vehicle prep process. The engine was always sort of lethargic, and I had chalked it up to the awful drive by wire calibration. When I did my 1st oil change I used 0w20, and the difference was immediate, and obvious. The engine was much more willing to rev, and had much better power in the upper revs than before. My theory is whatever weight/quality oil the dealership had used was messing with the vvti, not allowing it to operate properly. That was just my experience, YMMV.