Why does my car lose mpg?

I have 2013 honda civic why does it give me less mpg than before. I use to get 26-27mpg and now only 23mpg why if it's only 6 months old the car I've done 2 oil change only every 4500 miles since it uses synthetic oil and recently did tire rotation. How can I improve or should I take it to the dealer and fix it

Now you got used to the car and like the way it drives, your a more aggressive driver, with a heavy foot, so have fun

Why do you keep repeating all of your questions? Once will suffice. This is a huge pattern for you.

You need to realize the read out in your Honda is simply giving you an average MPG. For any given time period you make be racking up more city miles than highway. That in itself is enough to see a drop from 26 to 23 MPG. There's nothing wrong with your Civic.

That's an appallingly low MPG even at 26-27. Take it back to the dealer. Changing the oil and rotating the tyres should make virtually no difference.

I would advise you to:
1. Check your tire pressure every 4 days.
2. Make sure your Gas cap is closing properly and tightly
3. Change your Air Filter
4. Check your Spark Plugs(Often you can switch to more economic ones.)
5. Check your oil weekly, using AMSOIL you can save 6% on fuel cost as well as change your oil and filter once every 25,000 miles.
6. You should use a fuel injector cleaning system like
P.i. Performance Improver Gasoline Additive which you would use every 4,000 miles.

After following these steps you should see a large improvement in your vehicle's mpg performance.