Is it true that they can get "lazy" and then eventually go bad? If so,will they cause bad gas mileage if "lazy"? Will there be an increase in MPG if a "lazy" sensor or sensors were replaced? Ive read what the makers of O2 sensor manufacturers have written,now I want to hear what the techs have to say.

 

o2 sensor do get(lazy).they get old and cant react quick enough to correct fuel stratagy. and will quit working all together.