Someone told me that a new O2 sensor in my 1996 F150 w/ 302 would improve my gas mileage. If this is true I would be willing to do it but would like to save the money if it will not. I am skeptical because my check engine light is NOT on. Should it come on with a bad sensor, or does it wait until the bitter end? Thanks for your ideas!

 

When up to temperature and operating properly, the output of the O2 sensor moves around. Higher voltage for less oxygen (richer), lower voltage for more oxygen (leaner). If it goes above the high threshold and stays there, or if it drops below the low and stays there, then the Check Engine light will be turned on. If you don't have a check engine light on, I would leave it be if it were mine. FYI, the O2 sensor(s) are just one of many conditions that can turn the check engine light on.