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Poor MPG... sometimes

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Old Oct 2, 2006 | 07:55 PM
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Default Poor MPG... sometimes

I've noticed lately in my A4 that I'm ABLE to get 300 miles to a tank or around there if I do ONLY highway driving, but otherwise I BARELY get 200. It's really closer to 180, really.

My friend told me I might need to replace my thermostat, but I noticed this happening mostly after I seafoamed a few weeks back. I'm thinking I might have clogged up my cat or fouled an injector and/or plug, but I'm not showing any codes?

Maybe I'm just noticing it more now, but that's kind of low for miles to a tank isn't it?
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Old Oct 2, 2006 | 09:06 PM
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what do you have done to your car? and does it have any strange smells?
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Old Oct 2, 2006 | 10:25 PM
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weird, im getting some goofy problem like that too....
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Old Oct 2, 2006 | 11:00 PM
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I haven't done a single thing to my car and it doesn't look like any of the previous owners have either. The only stange smell I can think of is sometimes, very rarely, and very faintly, i can smell a bit of burning rubber but I've only noticed this like twice and it as almost impossible to smell. You couldn't even notice it until you stepped out of the car.
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Old Oct 2, 2006 | 11:19 PM
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My 02 Z28 is bone stock and gets the same mileage.
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Old Oct 2, 2006 | 11:47 PM
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well you dont see to be running that rich if there arent any smells, i have a A4 also and they tend to chug a bit more then the M6s....theres several things you can do to get the mileage up a bit....new air filter, fuel filter, check your plugs, and O2s...this might give it a little bit of improvement but like i said your not really showing any symptoms.....no smell, no bog, nothing like that....and please dont let your butt start telling you things.....just give it the once over in the departments i stated and check back with us
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Old Oct 3, 2006 | 09:59 PM
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i seafoamed mine and my mpg went down as well
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Old Oct 3, 2006 | 09:59 PM
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i seafoamed mine and my mpg went down as well
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Old Oct 3, 2006 | 10:06 PM
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maybe the cats are plugged up?
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Old Oct 3, 2006 | 10:18 PM
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ud have a smell typically
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Old Oct 5, 2006 | 04:08 PM
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thanks guys i think they might be too, it this gona cause any damage to my engine. im going with ory and headers in december anyway so cats r going bye bye
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Old Oct 5, 2006 | 07:00 PM
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I just replaced my thermostat and now im getting great mpg. I'll let ya know how many miles over the weekend.
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Old Oct 5, 2006 | 10:01 PM
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^^^ a hotter engine will tend to slightly take more fuel because its not running as effcient....seafoaming can do alot of good things for your car, but it also has some mixed results on other areas
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Old Oct 6, 2006 | 07:58 PM
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I cleaned my K&N filter recently and checked all my fluids - everything checks out but it's still happening. Maybe it's always been this way and I just didnt NOTICE but today, after my needle got to the quarter tank mark, it was empty by the time I drove 25 miles. That's not even an exaggeration.

I'm thinking it really might be a thermostat problem but I'm going to sound stupid saying this: Maybe my engine is running TOO cool? My temperature never gets to the first notch (thats like 180 isnt it?) it's always like 3/4 of the way to a quarter of full temp. Maybe my thermostat is stuck in the open position and its causing extra strain somewhere on my engine or... something?

I really can't think of why I'm getting such crappy mileage. If I did my math right, I should be getting at least 270 miles to a tank if the Trans Am gets ~18 mpg in city and has a ~15 gallon tank right?
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Old Oct 6, 2006 | 08:26 PM
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Seafoam killed the o2s in my old Z. I bet that has happened to you
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Old Oct 6, 2006 | 11:18 PM
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Wouldn't I be throwing a SES light if my o2 was shot?
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Old Oct 6, 2006 | 11:44 PM
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Originally Posted by Gallstaff
Wouldn't I be throwing a SES light if my o2 was shot?
Should be, but my Z didn't always throw it.
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Old Oct 6, 2006 | 11:56 PM
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your car would light up somewhat without the o2s....youd notice...
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Old Oct 8, 2006 | 12:27 PM
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If your 02's were bad you would notice the car to run better when cold, openloop than when it's gets up to normal temp. One way to check for a clogged cat is to hookup a vacuum gauge to the car and in neutral rev the motor up to 3k rpm. If the the gauge reading goes up then there's not any exhaust restrictions. If it doesn't go up or goes down then you have a glogged cat.
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Old Oct 8, 2006 | 01:02 PM
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I had a qlogged cat and my service engine light came on and stayed on.
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