It'* done took me like 5 min. to change it. The thing that botthers me is, ok when I first bought my car it was throwing a code for a bad O2 sensor, so the guy who owns the dealer said he would change it for free, so I was like ya go ahead and change it. But now that I took out my old one the head or the sensor part on the old one is a lot more narrow and small comparied to the new one. Are the earlier Bonn'ys (94-) O2 sensors differernt. I thing the dealer took one out of and older Bonny and sliped it in mine, the connectors are the same and screwed in the same but the end of the sensor is way different. Well, I'm just hoping my gas mileage will go up now.

Does anybody with an older Bonneville than mine who has changed their O2 sensor if there pretty small.

I changed my 88'* a little while ago.. The tip of it was just slightly smaller than the threads of it. The stock one was smaller though than the new one (old one was AC Delco, new one is Bosch.. bad choice from what I've heard. )

Well, maybe so, but to answer the original question: Depending on which AC-Delco O2 sensor you put in, its body may or may not match the old one. For my '93 SEEi, there were no fewer than three different AC-Delco part numbers listed as acceptable for it. One was a retail replacement part number that came in a box, the other two were dealer part numbers, and the one of those that was in stock came in a plastic bag. The boxed unit had a wide-body metal shell on it; the bagged unit (which I eventually bought, since it was $3 cheaper) had a narrower one, sort of like a spark plug.

I passed my emissions test the next day.

Well it was changed when I first bought my car cause it was throwing a code, but it got changed and the code whent away but never thought about it, but my gas mileage sucked.

Well now that I have changed it I have gotten a lot more miles on it. Before I would just get barely over 350 miles before my low gas warning came on, now when I changed it I got 350 with still 1/4 of a tank left and I used 1/4 of a tank before I changed it so I have gone 3/4 of a tank on the new O2 sensor and getting a lot more miles. I haven't filled up yet to check my mileage but I'm thinking it'* gona be over 21 like on the old one.