Mod (Ret.)

Since the o2's are one sensor out of a series of sensors that send a signal to the PCM for proper fuel/air ratio, then they could offer better fuel economy when replaced, but only if they are bad. As long as they are not setting a code, then replaceing them because they have high mileage would not provide you any cost savings, as the price of a set of O2's verses the savings you might see would not offset itself.