Bad MPG's With X-pipe????


New Member
Jul 2, 2007
Ok long story short I was getting 24mph before the swap and now I get 19, while shifting at the same rpm's same roads I can't afford this with the gas the way it is. Do x-pipes usually lower your mpg's? I have a check engine light so will that maybe make it run really rich? I just can't understand where all this gas is going????
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I seem to be having the same problem , I installed my O/R Prochamber last week and Im getting really crappy MPG !

I dont have a tuner yet , so I unhooked the rear O2 and plugged up the holes with bolts !

What seems to be the problem ?
Check out why the check engine light is on. That is probably the cause of the poor gas mileage. When I put a magnaflow X pipe on my car along with steeda cat back my gas mileage was up atleast 1mpg on avg and if all highway I was gettin 2 mpg better, as long as I didn't stomp on it to hear the exhaust lol.
I get crappy gas mileage, too, with my exhaust and gears setup. I used to get 27.7mpg on the highway, but now only about 21mpg. My car runs really really rich, or at least it did when I got it dyno'd. I've been meaning to get a tune, but I'd much rather get my intake parts first.

I've just learned to deal with it. Gas isn't really all that expensive in TX right now. Yes, it's more expensive than it used to be, but consider this: In Toronto, gas is approximately $4.25 USD per gallon. At $3.29 per gallon, that's nearly a 30% increase.

My point exactly.
I got 26-27 MPG doing 80 MPH on I-75 through the mountains in Tennessee and Kentucky a while back.

I have 4.10s as well. I'd get a tune if I were you guys.

I make decent hp and get great mileage with my MPH tune. :shrug:
I put shorty headers on, changed my H-pipe to an X, put super flow 40's on and changed my gears to 4:10's, my mpg went way down and my check engine light came on too. I took my car and did a dyno, it was running rich. He gave me three differant tunes and the only tune the check engine light does not come on now is when I have it set on my racing tune, more fuel, less air, which my car runs REALLY GOOOD on that tune, but she sucks gas bad! If I set it for more air and less fuel it runs like a 6 cyl. but it is good on gas.
secondary O2's are for emiisions OBDII. the computer doesn't adjust anything for them. it simply gives CEL. your x pipe can cause the mixture to outrange your primary O2's and cause the pcm to hunt. remember stock o2's are not wide band, you can get outside of their parameter range. a tune will fix it and turn off the secondary o2's.