02 Sensor

Went to the auto parts store yesterday and was asking about 02 sensors. The manual i have says they should be replaced around 100,000 miles. Mine is close. No check engine light on but I'd like to replace them for some preventative maintenance. The guy at the auto parts store said no need to change them until the check engine light comes on. Is this true or does he not really know what he is talking about? I'm all about saving money but my Cherokee is only averaging around 15 mpg right now stock and I'd like to improve it a little bit.

The guy at the parts store is just that-A guy at a parts store. If your waiting until the light comes on, fine, but it's better off to change before the computer can't see it anymore.

They don't always stop working, sometimes the voltage changes get slow and it's leaner and richer longer.

Personally, I'd change it. The possibility of helping out your gas mileage should outweigh the cost of the price of the sensor. There are lots of reasons to have low mileage, but changing out an O2 sensor is a good place to start.

I know it sounds kind of excessive but I change my 02 sensor every 2 years just before I smog it. New gas cap, oil & filter, clean & oil the K/N and making sure all the vac lines and grommets are in good shape too.

My1990 XJ with 220K on the clock failed smog miserably when I got it 7 years ago. It now passes with flying colors every time and really runs like a top, plenty of power, nice clean plugs etc. with all around mileage of about 18.