I have done damn near everything you can think of trying to improve my gas mileage. Pcv, air filter, fuel filter, checked for carbon build-up, tire pressure, removing junk, etc.
The only two things I’ve been able to see a difference in mpg with have been changing my spark plugs and having the roof rack off. I’m going to get a new front O2 sensor soon and see if that helps as well. Do the spark plugs if it’s been a couple years. I got 4 oem’s and didn’t spend more than $15.