2012 Honda Civic lx sedan mpg?

My Honda is getting horrible gas mileage, I'm averaging 20 city and about 35 highway. I wanted to know why I'm getting horrible MPG. I checked my air filter, but I don't know what else. Keep in mind that I just bought the car not even 2 months ago.

I don't know how you drive. If you are a little heavy footed that's ok mpg.
Use Cruise on highways. Check air in tires, run injector cleaner or a tank of Cheveron. If it has 100,000 miles it may need new spark plugs.

Unless you drive a full tank just in city, then one just in highway, you are just guessing. 35 highway is in line with estimations

Every motor that Honda makes has a common issue with the valves getting tight in the motor. They need adjusting every 60,000 miles or you end up with a bad idle, loss of power, and poor gas mileage. Have the spark plugs been replaced yet? Only use NGK or Denso brand plugs in your Honda.

35 highway is not "horrible", and you didn't buy a new car, so how is the fact you just recently bought it relevant?

It is rated a max of 38 highway, so getting 36 in real life is about right. City mileage varies a lot based on the conditions. I wouldn't say anything about it is horrible.