does anyone here change em at a certain interval? and where can you get em cheap?

i've heard o2 sensors fail quicker than spark plugs in stangs.

 

well if u were facing the check engine light problem, then just clean them and install BBK O2 eleminators, thats what ihave done to my car after i instaled the X-pipe.

click here

 

ebay, is a place you can get them pretty cheap. also try www.rockauto.com

 

o2 sensors only need to be replaced if and when they fail, not at an interval. Your check engine light will illuminate and give off a lean code... a good mechanic (yes that is an important part) will check your fuel trims to see if the o2s are switching properly and if they aren't... they will find out why. Could be the baro pid or even a vacuum leak... o2 sensors occosionally are the culprit but not all the time... just fyi.