alright i have a question can a bad o2 sensor cause bad gas mileage? i have a 94 dx hatch with a d15b7 with headers intake and apexi ws2 ..my gas mileage is pretty bad what can i do to increase it ..i know its have to go down cause of my mods but gosh..

 

yes it can

 

thank you i was trying to prove my friend wrong he states that a o2 sensor only is there to read the carbon monoxide leaving the motor and ect..and it has nothing to do with the gas mileage and i was trying to prove him wrong thanks..if i could have more replies it would be great