Do i have a lemon car? Q50 low mpg even when babied

I purchased a certified pre-owned infiniti Q50 AWD prem 4 months ago with 12k miles on it. It has a bad history of oil change, it had its first oil change at around 10k. Then changed again after purchase. I drive 50% city 50% hwy. I'm getting 15 mpg. That goes for gear shifting at 2k rpm, i rarely floor. But compared to the advertised 22mpg, 15mpg is far from it. I reset the counter and went from philly to nyc and got 22mpg, that meant highway only. I went to the dealership and had it checked out only to get an answer saying everything is "fine". Clearly it says 15mpg which is far off from the 22mpg advertised. I have reset the ecu also.I came here for advice a while ago and i appreciate everyone that helped out. Got my car tire rotated, 4 wheel aligned, maf cleaned, 35psi recommended tire pressure, and clean air filter. Most of all i babied the car. I decided to calculate my q50 mpg on paper and got roughly ~10mpg for 50 miles which in return uses 5 gallon of gas. I went on fulley.com and mostly everyone is getting 18-19mpg.Back during the time when i was selecting my cpo q50, there was a puncture hole on the bumber of my selected car. They purposely hid the puncture on their gallery. The dealer insisted to sell it to me at a solid price of 30k with no reduction. I refused because im not buying a cpo car just to get it repaired the next day. The manager comes out and talks about having 2 of the exact same model and trim in the back of the parking lot. Stupidly enough i purchased one of those 2 car because from the outside it looked perfect. At the time those 2 cars was not listed online or in their online inventory as used car.Could this be a lemon car? I went to the dealer to check for the mpg problem. They diagnosed it and got 16city / 25highway with no error. They insisted it is the way it is and nothing could be done. I get ~10mpg from my own calculations and 15 from the avg mpg counter. This cant be right unless someone can explain otherwise. What can i do about it? via /r/cars http://ift.tt/2u2Wuw8