The only issues I've ever had were a 2012 Challenger and a 2015 Wangler with the 3.6 what would occasionally puff a cloud of terrible smelling smoke (it smelled both like unburnt fuel and oil at the same time, and I could never decide if it was dark gray or black colored). It was really only noticeable when you started the car and backed through it, worse in the Jeep because it was usually open. The dealer could not replicate on the Challenger. The Wrangler got so bad it finally tripped a check engine one day after doing that. I should have read the code, but I was planning to sell it anyway to move to Pittsburgh, so I simply erased the light and traded it off. Both these vehicles were in the 15k mile range when this got noticeable. I've had others than never did this.