How many sensors should I change after 90,000 miles. My light comes on at lower speeds, then goes off?

 

If you want to throw money away replace all of them. Otherwise why not check for codes yourself.

What year/model/engine/transmission vehicle are you referring to?

 

I guess I got worried when I saw the Chilton book suggesting that at least 4 of these sensors be replaced every 15,000 miles. I did actually go down and talk to a mechanic, he said it was the oxygen sensor, no worries unless you want to please the EPA. Thanks for your reply, Randall Ford (yes that is my real middle name)

 

The O2 sensor does more than keep the EPA folks happy, it will make your wallet happy too by delivering better fuel economy.

You really should get a handle on what code(s) are happening then repairing the root cause.

 

Yeah, a faulty O2 will cause many more problems one is wanting to deal with. Get a code reader, verify what is going on and if possible, replace sensors with Motorcraft parts, not cheap knock offs. You can even check for cods with a paperclip if needed too for free.