pinging , poor mpg 2015 optima

Hi there, I have 2015 kia optima 2.4L with 70,000 miles.
I do most of short distance of 10-15 minutes a direction a day to school and back.
On the highway I am getting 24MPG and around 2000 rpm i can notice pinging noise.

I used to fill up with cheapest fuel in town (Tarzana / LA CA) and now I moved to Costco gas just in case.

I have the OBDII code and diagnostic reader (I have video) and I wish someone can give me a clue what would be the fix for this. I wish I can post the video here so it show the values of the different sensors.

Thanks much