O2 sensor

1993 LeSabre 130,000 miles

Is there any reason I should replace the O2 sensor at 130,000 miles if all indications are it is working OK? (24 mpg highway)

I wouldn't.

Unless you see indications that it isn't working (like bad mileage or raw fuel in the exhaust pipe) and the CEL isn't on.

O2 sensors work by changing voltage (as little as .1 volt) when running lean or rich. In normal operation, the sensor's voltage is constantly changing. The ECM will set the CEL when that voltage is constant (always rich or always lean).

The tip of the O2 sensor is flash plated with a noble metal (??platimum) giving it the electrical property of changing voltage in the different exhaust environments. Because the sensor lives in the hot exhaust, they fail when the noble metal eventually wears away or is coated over with exhaust contaminants.

my o2 died at around 230k... original AC DELCO, i replaced with a bosch.. but I suggest that you change it out before it completely dies. It will increase your gas millage even more... i waited till mine completly died, and car was sluggish. o2 is important, and should be changed every 60k miles, for best performance. Bad 02, equall bad signal from ECM to the fuel injectors...