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Old 11-01-2006, 02:23 AM   #1
jmart69x
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Default Poor Gas Mileage - 2006 Mustang GT

I have a 2006 Mustang GT 5-speed. Fully stock, I got 17-18 MPG city / 21-22 MPG hwy. A few months ago, I had MAC mufflers installed. My MPG plummeted. Now I have been experiencing 12-15 MPG city / 19 MPG hwy. Everyone says it must be my driving habits, due to the new sound I must be heavier on the pedal. I have NOT changed my driving style. To prove the point, I tried driving agressively on one tank vs driving mildly on another tank. No difference in MPG! Still 12-15 city/ 19 hwy. I brought the car to the dealership and they told me that the "Break-in period" on the engine is 10,000 miles. They stated that since I have 9,500 miles, I could expect a fluctuation in miles and that the the advertised MPG of 17 city/25 hwy is a range that could be affected by weather, gas quality, etc... They further said that unless the "check-engine light" is on, they would not find anything. Then, a tuner suggested that I try disconnecting my battery overnight to let the computer reset itself. I am a little skeptical, but am considering it. Has anyone ever experienced this? How did you remedy the situation? Would disconnecting the battery rectify this odd situation? What else could the problem be?
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Old 11-01-2006, 09:30 AM   #2
Haze28
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Default RE: Poor Gas Mileage - 2006 Mustang GT

I was wondering the same thing, I have about 1300 miles on my car and am only averaging about 14mpg. I was hoping to get a little better than that.
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Old 11-01-2006, 10:53 AM   #3
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Default RE: Poor Gas Mileage - 2006 Mustang GT

Hmm...that mileage does seem low.

Try the computer trick. It's easy and it can't hurt anything.

These cars have an ECU feature that "learns" driving styles and adjusts the drive-by-wire system to suit. Many people report improved throttle response and power after doing the battery disconnect trick....
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Old 11-01-2006, 11:33 PM   #4
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Default RE: Poor Gas Mileage - 2006 Mustang GT


Quote:
ORIGINAL: CrazyAl

Hmm...that mileage does seem low.

Try the computer trick. It's easy and it can't hurt anything.

These cars have an ECU feature that "learns" driving styles and adjusts the drive-by-wire system to suit. Many people report improved throttle response and power after doing the battery disconnect trick....
Yeah definatelt try diconnecting the batter, I have also heard that it has helped people. Those numbers are low becasue I get about 21-23mpg and drive her hard a few times a week.
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Old 11-01-2006, 11:53 PM   #5
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Default RE: Poor Gas Mileage - 2006 Mustang GT


Quote:
ORIGINAL: jmart69x

I have a 2006 Mustang GT 5-speed. Fully stock, I got 17-18 MPG city / 21-22 MPG hwy. A few months ago, I had MAC mufflers installed. My MPG plummeted. Now I have been experiencing 12-15 MPG city / 19 MPG hwy. Everyone says it must be my driving habits, due to the new sound I must be heavier on the pedal. I have NOT changed my driving style. To prove the point, I tried driving agressively on one tank vs driving mildly on another tank. No difference in MPG! Still 12-15 city/ 19 hwy. I brought the car to the dealership and they told me that the "Break-in period" on the engine is 10,000 miles. They stated that since I have 9,500 miles, I could expect a fluctuation in miles and that the the advertised MPG of 17 city/25 hwy is a range that could be affected by weather, gas quality, etc... They further said that unless the "check-engine light" is on, they would not find anything. Then, a tuner suggested that I try disconnecting my battery overnight to let the computer reset itself. I am a little skeptical, but am considering it. Has anyone ever experienced this? How did you remedy the situation? Would disconnecting the battery rectify this odd situation? What else could the problem be?
Are you measuring your gas mileage or just going by the computer? To get 12 mpg while driving easy would require a very rich a/f ratio, which you would think would set off a check engine light. If 12 mpg is your actual measured fuel mileage on a full tank of gas to empty, then I'd be looking for a fuel leak. Does the engine start easily?
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Old 11-02-2006, 12:26 AM   #6
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Default RE: Poor Gas Mileage - 2006 Mustang GT

I have been measuring my MPG by resetting the trip info meter each time I gas the car up. Have not noticed any fuel leaks. Car starts up no problem. Dealership supposedly did a diagnostic and confirmed that the car averages 14 MPG (No ****), but couldn't offer any helpful assistance- total waste of time dealing with the dealership and their attitude. I will try disconnecting the battery. I'll keep you all posted on my progress.
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Old 05-18-2008, 12:26 PM   #7
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Default RE: Poor Gas Mileage - 2006 Mustang GT

How excatly do you do the disconnet the battery trick?
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Old 05-18-2008, 01:03 PM   #8
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Default RE: Poor Gas Mileage - 2006 Mustang GT

with my 06 gt stock except flow masters i was getting around 14 city and 24 hwy. after all the mods including gears i get around 12 city and 21 hwy. i am quite heavy footed also. your in town mpg at 12-15 seems normal. your hwy at 19 mpg seems low.
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Old 05-18-2008, 01:19 PM   #9
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Default RE: Poor Gas Mileage - 2006 Mustang GT

Quote:
ORIGINAL: cwhite7

How excatly do you do the disconnet the battery trick?
8 mm socket on the nut for the battery terminal connection

loosen the conection and pull it off

put it back on in the morning or a few days later
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Old 05-18-2008, 01:25 PM   #10
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Default RE: Poor Gas Mileage - 2006 Mustang GT

In order to measure the proper MPG on the highway, you must make a fairly long freeway run. With a full tank of gas, not topped off, which means you don't fill it to the brim just before it overflows, drive 100-200 milesnon-stop on the freeway and refill it using the same method. Using the same pump and station would be great but not always convienant. That's how you get the best estimate of your fuel consumption.

Compare against your cars computer and you will see if there is a difference.

I know when I fill mine up there is always a slight difference in how much fuel the computer says I used and how much I get at the pump.
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Old 05-18-2008, 01:25 PM
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