I've heard nothing but good things (GREAT things!) on the 3.6L Pentastar motors, but not sure if there were early teething problems with them. My first one was on a 2012 300, then a 2014 300, & my current driver is a 2016 300. ONLY problem I had was the oil filter housing cracking & leaking on my 2014 - this was a VERY common problem. You'll start smelling a strong oil burning smell - smelled to me like I cooked a belt or something rubber burning. Chrysler did that repair - that was a TSB I'm pretty sure.
I recently read an article about the 3.6L engine being rated a world-class engine. They talked about fleets running these with over 600,000 miles on them, & Chrysler tore-down the motors & said there were virtually no signs of wear internally - the cylinder walls even still had the cross-hatch pattern still.
Otherwise a very good engine. FCA really screwed up not correcting the issue quicker! A silky smooth, powerful engine, and had they made a quick correction, they would have kept from damaging the reputation. There's now a class action suit with the van owners because FCA not honoring this warranty for them and they aren't happy
https://www.classaction.org/news/fc...-for-pentastar-v-6-engine-ticking-defect
