Personally, my gas mileage isnt the greatest, and I feel like the original owner of my 00 never replaced the o2 Sensors in the car. Am I supposed to wait until I get CELs or would they be functioning fine until cels show otherwise?

Also o2 sensors are universal right? As in, it shouldn't matter whether its downstream or upstream?

 

i waited until the CEL came on and they are not universal.

 

dont replace it if it's not broken. Take your car to auto zone or some place like that and have them check for pending codes. This may give you an idea of any sensors like the o2 or knock sensor that are on their way out

 

If im not mistaken,they are bank specific. I wouldnt worry about the o2 sensors if theyre not showing codes BUT i would replace them in sets ie: upper and lower banks when they do go out.

 

02 sensors can get lazy for lack of a better word, they won't through any codes but will effect the operation of the car, when where the spark plugs changed? they will also effect the cars performance ... have you ever cleaned the MAF sensors? there are a multitude of things that can effect the fuel economy, bad or soft tires weak old plugs lazy 02 sensors, dirty carbon build up inside the engine (a good seafoam treatment followed by changing the oil can help cleanup the inside of the engine).

 

o2's will almost guarantee to be a waste of $ in search for better MPG.

Replace air filter
Replace spark plugs
Clean MAF
Run proper 91+ octane fuel
Make sure (especially rear) brake calipers are not dragging

On my 5.5, after I went through all this, I'm getting way better mileage.

I can drive back and forth to work (90 miles) with the fuel gauge still showing above the F. I havent calculated actual mileage yet, but by looking at the rate the gauge drops, I can tell it's improved. Also, the CRC MAF cleaner is like a supercharger in a can. I gained so much power back from using that, not even funny!

 

Interesting, keep us updated on the actrual MPG (after a tank).

OP, whats the MPG you been getting?

 

A 6mt will do that for ya.. A auto totaly different story

 

I used seafoam once, and it worked great... for a while. Now I get around 16mpg city/highway mixed. I'm going to do everything on the list that was just posted and will post if anything improved!

 

I changed my rear 02 sensors because of a code and the fact that I had 175k and what a difference it made intiatially. Definitely helped the MPG rating. Seafoam FTW aswell