I've noticed that recently (maybe because of the chip) my mpg is not good at all. The average mpg is about 18-18.5 and i got ~23 before. I know it's getting colder out and the winter fuels probably hit the gas stations but i don't think that should cause a drop like that. I got the revo stg 1 flash and changed the plugs w/ ngk bkr7es. I have not gotten any cel's. I did run seafoam through the car a few weeks ago but that didn't seem to help anything. I also added some of it to the gas tank and i'm still on most of that tank. Could that be a possibility? The airfilter doesn't look bad either. The car has about 100k miles and probably on original o2 sensor. Would this be the most likely cause? Could the car be running rich and if so is that easily adjusted especially since u can tune with lemmiwinks(sp?)


I'm not driving around stepping on it either. When ever you accelerate it's not uncommon to see the mpg hit 13 and going up hills the same thing happens if not worse. When i'm not accelerating or at highway speed it seems to be much better.

 

I'm pure stock (701N DV adnd K&N panel). I have 66k miles and get 21 city 25-26 blend 30+ highway. I also did a seafoam at last oil change and run the same plugs as you.

I doubt it's seafoam and I hear flashes help the mpg a bit (though you tend to step on it more and thus lose the benefit). Have you cleaned your MAF? O2 sensors might be a contributor - the easy way to tell would be hooking up to a VAG. That is what you really need to do. You can check your deltas and see if the MAF is off, if your O2 sensor is goin', etc.