Ok folks my car is a 2004 with 170 000 miles. I normally shut the car off at red lights early in the morning as the auto stop only works when the engine warms up. I do have quite a few lights to deal with before I get to the expressway on my way to work so I did my usual engine off. As I restarted after my third red light I believe I gave her gas a little to soon, she vibrated then lunged forward and we were off to the next light. By the time I got to work my check engine was on. I have a code reader at work so I checked and got O2 sensor bank 1 trim 1. I am sure it must be the front side or upstream as some refers so I called the stealer and they want $550 for both. Can I just change one or do we have to change them in pairs? Can getting into the gas too soon on a restart destroy O2 sensors or was it probably just time? Six days ago on my last fill up I got v power 93from Shell thinking it was going to get me more mpg, does anyone think the change of gas had something to do with it? I will wait for some experts to chime in before I make my next move but I really cant wait for my next fill up to go back to regular 87. Now with my check engine on I can only manage 39mpg down from my usual 47mpg. Please send me your suggestions, thanks....I have posted this elsewhere but got no response, please all suggestions welcomed as I am sure others will point me on the propper track.