O2 sensors not only go bad, they typically become less reactive long before they fail. The RX-7 does not alert you of an out of tolerance O2 sensor. --On 1984-88 models, there is not even a check engine light to tell you that sensors have failed. The consequences of a substandard oxygen sensor are poor fuel economy and a lack of smoothness at cruise. With an RX-8, the check engine light will stay on and may prevent you from passing a smog test.

 * Restore fuel economy

* Smoother / cleaner running

* Emission compliance