I’m getting low gas mileage. We recently changed the air filter. Then cleaned o2 sensor, throttle body, spark plugs, and catalytic converter. The engine is in good condition. Average mileage is near 9.7
First Step
The first thing to do would be to see if there are any check engine light codes present. Next post the codes below and we can determine which codes may be effecting your fuel mileage.
What kind of mileage were you used to getting? Is this why you started throwing new parts at it and cleaning everything?
Have you tried fuel from a different station to see if there was a difference?
Possible causes
If you are letting the car warm up before driving it will decrease. Low tire pressure will also decrease fuel mileage. A clogged air filter or dragging brake caliper will also decrease fuel mileage.
Source: https://www.freeautomechanic.com/mechanic/forum/tag/fuel-mileage