Bad gas mileage

Hello, I'm Danny.

I would suggest performing a tune-up. I would start with changing the spark plugs and fuel filter. Here is a tutorial showing how to perform a tune-up:

https://www.2carpros.com/articles/how-to-tune-up-a-car-engine

Here is the tutorial for replacing a fuel filter.

https://www.2carpros.com/articles/how-to-change-a-fuel-filter

I've attached picture steps below how to change the spark plugs and fuel filter for your car. It also show the spark plug torque and gap. Hope this helps and thanks for using 2CarPros.