o2 sensors

anyone know an easy way to replace the o2 sensors/where to get a good deal on them...will replacing bad ones give you better performance/gas mileage????? thanx

if theres a napa near you go there i went to the mazda dealership and they told me $360 for both of them i went to napa and they had some bosch ones for $65 a piece bought them both and got them installed for $40 at my mechanic and my check engine light turned off and i passed smog

thanks! yah i did some searching and found some for about the same as yours and my mechanic also charged me $40. Thanks for the advice!