My girlfriend bought a 2002 Sunfire 2.2 with 32,000 miles. The gas mileage is only about 20mpg. Her old 96 Sunfire got about 32. I replaced the spark plugs, air and fuel filters and added fuel injector cleaner to the gas. So far no change. No check engine light. Anything else I could check?

Steve

tire pressure and alignment....

tire pressure and alignment....


Tire pressure is good and alignment seems good. No abnormal tire wear and it tracks nice and straight when you let go of the steering wheel.

Can the O2 sensor be bad and not give a Check Engine Light?

Pull any trouble codes and fix. Some will not turn on the light. Then look at the live data short term and long term fuel trim and how the O2 sensors are working and tell us.