Sudden large decrease in gas mileage - no mods :<
Brand new Direzza's, 2 weeks old, balanced, inflated, and alignment done. Brand new plugs, 2 months old.
I have just under 13k miles on it.
I don't have a problem boosting, but I'm not always in the boost either.
I did an oil change today, also cleaned, re-oiled the air filter, used an octane booster/fuel treatment, just to be on the safe side and do the easy, DIY things I could think of.
If it's a bad O2 sensor, how do I get that checked short of taking it to a dealership, is it something I can DIY?
I have just under 13k miles on it.
I don't have a problem boosting, but I'm not always in the boost either.
I did an oil change today, also cleaned, re-oiled the air filter, used an octane booster/fuel treatment, just to be on the safe side and do the easy, DIY things I could think of.
If it's a bad O2 sensor, how do I get that checked short of taking it to a dealership, is it something I can DIY?
Maybe you have a bad o2 sensor (front by the turbo).
Also I've noticed driving with my windows down has a negative effect on MPG's about 2-3 mpg decrease (mostly 45 mph driving).
With easy accelerations, windows up, and low traffic mostly 40-45mph cruise I get about 27 MPG. In heavy traffic conditions it goes down to 21 mpg sometimes.
Also I've noticed driving with my windows down has a negative effect on MPG's about 2-3 mpg decrease (mostly 45 mph driving).
With easy accelerations, windows up, and low traffic mostly 40-45mph cruise I get about 27 MPG. In heavy traffic conditions it goes down to 21 mpg sometimes.
about 4-5 mpg less 
Evolving Member
Joined: Nov 2006
Posts: 129
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From: CA
Put the OEM filter back in for a peace-of-mind. Drive slower, then recheck your gas mileage. Check to make sure you don't have a gas leak! Good luck!
Last edited by TRUE-GRIT; Oct 6, 2007 at 07:15 PM. Reason: update
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Newbie
Joined: Mar 2007
Posts: 91
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From: Tri-State Area
i think bad o2 sensor. in my tsi when the front o2 sensor was almost dead but not completly dead (my cel never came on) i could barley get 20 mpg. Ever since my new o2 sensor was in i can drive quicker and harder i can avg about 25-30 mpg
190 is when my gas light comes on. and thats where it has come on for the past 45k miles. the only time i get 240-260 on a tank is when i am on a long haul... vegas to LA.
KNN can sometimes be over oiled. you should clean it when its new. then lightly re-oil it. I have always done this and have never had a maf issue.
KNN can sometimes be over oiled. you should clean it when its new. then lightly re-oil it. I have always done this and have never had a maf issue.
Is it obvious when the tire pressure is off on the stock advans? I only have 7k on my car and I've noticed a bit of a change in my mpg, but I'm chalking it up to the fires here and a dirty filter. But my dumb self hasn't checked the tire pressure yet.
Maybe you have a bad o2 sensor (front by the turbo).
Also I've noticed driving with my windows down has a negative effect on MPG's about 2-3 mpg decrease (mostly 45 mph driving).
With easy accelerations, windows up, and low traffic mostly 40-45mph cruise I get about 27 MPG. In heavy traffic conditions it goes down to 21 mpg sometimes.
Also I've noticed driving with my windows down has a negative effect on MPG's about 2-3 mpg decrease (mostly 45 mph driving).
With easy accelerations, windows up, and low traffic mostly 40-45mph cruise I get about 27 MPG. In heavy traffic conditions it goes down to 21 mpg sometimes.
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