Here is my 2 cents since I have this engine (the maxed out version) in my '14 Ram. Great engine BTW, good combo or towing, power and gas mileage.
Ok, my filler cap and manual says 5w-20, but if you download the "full" manual, there is a loop hole that allows 5w30 if 5w20 is not available. It doesn't mention 0w-20. The engine was originally designed for 5w30. If you do not tow or do not drive spirited often, you will not see any difference in wear between the 5w20 and 5w30. I live in a mountainous region, so my engine can be under a load at times, due to this I use 5w30. I know my manual says the sump is like 5 3/8 quart including the filter, but what I have found is six quarts does the job according to the dipstick. Now with this engine, the oil seems to be slow about draining back to the sump after shutoff, so if you check your oil level, make sure you give it about 30 mins to settle, even the dealership screwed this up for me by not waiting and adding an extra quart to what I already had, but not enough to harm anything.
So far, I have used 5w-20 havoline pro DS, did fine, used 5w-30 QSUD, did fine, Castrol Mag 5w-30, did fine, Napa Syn 5w30, again did fine. I haven't noticed any difference in power, acceleration or fuel mileage when I went from 5W20 to 5W30. So far I have ran NAPA the most due to their sales before the year ended, really liking the oil. I tend to stick to semi syn or synthetic oils, just what I prefer, but I am thinking that the oil that came with it from factory was pennz yellow bottle. Choice of filter seems to matter with this engine, I hear lifter tick for a few seconds on a cold start with everything but the mopar filter. I may scale back to 5w20 again and see if I still can't notice a mpg difference.
As far as issues, the only one, that isn't limited to the 3.6, that's becoming common, is the oil pressure sensor failing. If that happens I hope its still in warranty lol because you have to remove the intake manifold just to reach it. Luckily mine was still under warranty. Haven't heard many complaints about the cracked heads issue since Chrysler Fiat addressed it before the '14 models rolled out.