Your fuel mileage looks great to me. The 2.4L is EPA mileage est. (cty/hwy) of 21/28 mpg. Mileage really drops off going 85 vs going 70. Anytime you get EPA mileage numbers, your doing great because most manufactures pump these numbers up.
What brand "code reader" are you using to plug into the port? If you did not spend at least $100.00 or more for a low end "scanner", I doubt the reader is capable of doing testing. Anything less that $50.00 is just a code reader and not very useful for doing any real diagnostic work on a vehicle. These cheaper reader use the old ELM327 chip or some variation of it. If you Google "ELM327" or read more about the chip here: https://en.wikipedia.org/wiki/ELM327
. Be sure to read the part about the "Pirate clones" of the ELM327.