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Discussion Starter #1
No CELs, engine is running great, but my fuel economy blows donkey penis. Sixteen mpg city, using no A/C. My only power enhancing mods are bored TB and the CP-E intake kit. Automatic tranny. Fuel trims must be within spec, otherwise I'd be seeing a CEL, right?

Bone stock I was getting at most 21mpg, and then with each hp mod (first the CP-E products, then the TB) the mileage dropped an additional 2mpg. I'm guessing my car makes at most 240bhp and I dont see how that should be using so much gas.

I've been exploring several explanations for this horrendous economy, but so far no answers, so I'm throwing this out to the group. Am I the only one getting such shit mileage?
 

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Well my average went from 23 mpg to 19mpg for the past 2 months, but that's also because of my 99.999% city driving now. Haven't seen 16mpg yet and hope not to.
 

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My fuel economy took a significant hit with the change to an ethanol blend in the fuel in Texas. When it went from 0 to 10% my fuel mileage went down by 2-3mpg. The ethanol blend should have only decreased my mileage about 0.5mpg, but something about this engine made it go down considerably more. Particularly odd since the Duratec30 (when properly equipped) is a flex-fuel engine.
 

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Yeah, my mileage has dropped from about 22 mpg (city) bone stock to 19.5 mpg with the CP-E intake and now it's around 17.5 mpg with no additional changes to the car for the last 6 months or so. :headscrat: It gets considerably better highway miles but this still has me wondering what's up. It's not just you...
 

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Sorry to hear about the drop. I really don't see where either of those would cause a drop like that. Especially the Intake, since it should free up horse power instead of force the car to hog more gas. I would talk to my dealership. Well, that is if they are worth a crap. Most will BS you right out the door. Could it be your O2 sensors, or a sensor like the MAF? To be honest I don't even know if our car has a MAF. Just ideas to try and help.
 

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i'm just gonna throw out some ideas here:

-is your air filter clean?
-PCV valve not functioning properly?
-spark plugs/ ignition system need a tune-up?(from what i understand spark plug misfiring can cause up to a 25% decrease in gas mileage.)
-belts not adjusted properly?

that's all i can think of @ the top of my head..., but i do like the "ethanol gas" theory.
 

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Discussion Starter #7
I really don't see where either of those would cause a drop like that. Especially the Intake, since it should free up horse power instead of force the car to hog more gas. [/b]
But that's assuming there's no lead foot associated with the hp gains. :D

i'm just gonna throw out some ideas here:

-is your air filter clean?
-PCV valve not functioning properly?
-spark plugs/ ignition system need a tune-up?(from what i understand spark plug misfiring can cause up to a 25% decrease in gas mileage.)
-belts not adjusted properly?

that's all i can think of @ the top of my head..., but i do like the "ethanol gas" theory.
[/b]
Filter is clean, no oil loss so I'm sure the PCV is fine (never seen one stuck closed), havent pulled the plugs, but the idle is fine and the engine pulls great, so I dont see how they could be at fault, and I checked the belts yesterday, no problem there.

No mention of any ethanol addition in the news in Atlanta so it seems unlikely that's the culprit.

Yeah, my mileage has dropped from about 22 mpg (city) bone stock to 19.5 mpg with the CP-E intake and now it's around 17.5 mpg with no additional changes to the car for the last 6 months or so. :headscrat: It gets considerably better highway miles but this still has me wondering what's up. It's not just you...
[/b]
yeah you're not actually that far behind me. This car get's fricking awful gas mileage. Damn.
 

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check your air pressure, should check at least once a week
 

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I get barely 20 mpg, 80% city with a granny foot, but al least I have an excuse. I run the a/c all the time, because 11 months out of the year it's freakin' hot here in FL.

Air pressure fine. 34psi cold.
New air filter.
Oil fine.

If i knew i wouldn't be taking such a hit on depreciation, i might consider an 07' Mazda3.
 

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Discussion Starter #10
check your air pressure, should check at least once a week
[/b]
pressure is fine too.

Either the problem is something really exotic, or my particular 6s just gets crap fuel economy.
 

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That does sux...

I just took a trip in mine, and over the trip I got 25, 23, and 23. Which was of course mostly highway, but I did run up and down 3 mountains and drive around town some. The running up the mountains would have caused a huge drop I am sure, but the average remained good. I normally get around 21ish with my daily mixed driving. This is with a stock 03 6s MTX tho...

As far as the 10% alcho... They passed a law here that says you dont even have to post that your selling it vers. regular gas. So you could be using it and not even know it.
 

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I too have had the 16 mpg problem in the past months. For a while after i used a system cleaner it went up to about 18...now its about 17....argg i cringe everytime i read someone saying "Oh yeah, you know. My mileage hasn't been that good. 22 mpg or so in the city". If you find a solution willow...get it posted...i don't even wanna know how much money im burning up every month...
 

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I'm consistently getting 20+ I might dip down to 19 when I am leading footing it around on city streets. A lot of my driving is freeway, but 50% is in moderate to heavy traffic. I think my average hovers around 21 mpg over time, though I can get into the upper 20's when I do long trips on the cruise control. I have the injen running on the cp-e map (not the injen fix map) with Hankook Z212 RS2 (read: sticky), MTX and a moderate heavy foot. Cruising speeds on the freeway are ~80-85.
 

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do you have atx tranny or is it just automatic? if atx try using manual more, i save about 1/8 of a tank per trip on my commute that way.
 

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Why is anyone crying..... Gas prices have taken a nose dive recently!
 

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For me, the difference in mileage between driving conservative and driving spirited is minimal, so I stopped keeping track. Maybe my conserative is not that conservative though. The way I figure it, I have to drive my car and I like driving in a spirited manor most of the time, so there isn't much point.
 

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Discussion Starter #17
My fuel economy took a significant hit with the change to an ethanol blend in the fuel in Texas. When it went from 0 to 10% my fuel mileage went down by 2-3mpg. The ethanol blend should have only decreased my mileage about 0.5mpg, but something about this engine made it go down considerably more. Particularly odd since the Duratec30 (when properly equipped) is a flex-fuel engine.
[/b]

I just verified that my favorite retailer began selling a blend of 10% Ethanol a few months ago. I always fill up there, so I assumed that incremental drop has due to my last mod.


Now I just need to find a Tier 1 retailer who isnt pushing fricking Ethanol!
 
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