I drive an 05 Si and i get 23-25 MPG stock. I have a faulty 02 sensor that needs changing but I've heard mix reviews on whether or not that effects MPG. I don't drive bad I'm not sure if I should be getting better mileage or not? Tips?

 

a faulty O2 sensor WILL NEGATIVELY EFFECT your gas mileage. period. end of discussion.

if you want better gas mileage, fix your O2 sensor.

 

You could probably squeeze 5mpg out of it by changing out that 02. If you go to Advance Auto Parts they rent you a tool for free ($30 returned deposit) for removing the 02 censor. A normal ratchet won't work because the wire for the 02 censor gets in the way. This tool has a simple slot and attaches to a ratchet.

 

$30 for a tool? You can buy the tool to take it off for $10. Lol I had to change my front end O2 Sensor a few months back and just bought the ratchet for it.

 

the 30 dollars is a deposit, you get the money back when you return the tool. therefore its free.... which is better than 10 dollars for a tool you'll probably only use once.

 

Ah well I'd much rather just buy my own tool, you never know how much you will need it and it's much better to just have your own, but free is good too

 

You should be averaging 26-28 MPG, driving normally. If you normally shift at 6000 rpm then no, your mileage won't be nearly as high.

 

My boosted 02 si gets 20 city

 

that's pretty good