MPG, yea I know, another one.
 

Well I know there are other threads about this, but i've searched for about 45 mins now and can't find the answer I want.

I filled earlier tonight at home before i drove back here to college. Its about a 2 hour drive, there is one town to slow down through and 1 on ramp to get on the interstate, other than that i was on cruise control the whole way, no other turns and ND is flat land. 65 mph exactly on highway, 75 exactly on interstate, which are the speed limits. I filled right away after i got off the interstate here. 23 mpg, wtf? I have the 2.4, it should be better than this on highway.

So question i couldn't find, which O2 sensor has most to do with gas mileage? I have 109,xxx miles and they have never been touched, so i'm going to try them. I have a new air filter, new fuel filter, and new plugs 10k ago (ACD plugs). 34 psi in my summer tires. Any opinions on anything else that could help? I'm going to clean my MAF tommorow, and try zmax for the hell of it.

run an injector cleaner through your gas. (i tend to do that once a year)

upstream O2 affects mpg the most...iirc.

hmm... thats pretty harsh, i get better mpg on my V6. :eek:

The oxygen sensor behind the catalytic converter solely monitors emissions. Nothing else.

The oxygen sensor closest to the engine is what controls closed loop fueling.

I feel for you, my 2.4L gets about 22 combined on a good week (driving to and from work on a 45mph road, not too many stops). I figure I wouldn't save enough money in fuel by replacing an oxygen sensor. Maybe I could remove the back seats. :)

Will say, though, the upper speeds aren't usually good for gas mileage, hence the "drive 55" thing back during the Arabian oil crisis. Force required to overcome wind resistance (drag) is the square of velocity so the engine has to push harder; just compare your tach between different speeds. On a flat road I think I average about 1800rpm going about 50 and 2000rpm going 60 (off the top of my head).

yea i did replace my 02 sensor, but the $20 universal one i put in was shit so i took it out and returned it. i cleaned my TB good and my IAC, also ran the zmax system for the hell of it, and now i get like 25 lol, but in that time they switched to winter gas and it got damn cold, so i can't really know if it helped til next spring now.

the guy i had scan it quick at home said it was running rich, but i have no idea what else could be the problem. the stock o2 sensor is actually putting out the correct voltage according to the scan tool, so that shouldn't be a problem.

yeah i got the v6 i get 31 straight highway and about 22 to 28 mixed