Perhaps some more details would help. Daily driver, stored (how long) , mileage, year, transmission, check your oil level and color, how long have you had it, Certified, warranty, etc. The more you provide the better the people here can assist you. Was it a knock or a ping? How did it perform under a load on the highway?

In regards to your dealer changing the oil, well if it was me I would get a new fleece filter and 0-40 Mobil 1 and that way you are sure. Funny thing happened to a friend, he picked up the car from the dealer and I was with him and I asked the detail guy who just drove it to get a full thank of gas in it for the delivery to the new owner what grade of gas he put in it. He proudly told me all the cars here take unleaded regular. Most Chrysler dealers have no clue what is supposed to be in this car. I'll let you draw your own conclusions on the oil and gas issue.