What's the best fuel for 2021 Honda Civic?

What is your question?

You I have a 2021 Honda Civic LX. I've only had it a couple of months and when I first got it, I filled the tank with 89 gasoline. After the tank was almost empty, I went to 87 because people said it wouldn't make a difference. Well, I've noticed that my mpg has gone down since using the 87. Should I go back to 89?

How long has your 2021 Honda Civic had this problem?

2 months