Significant reduction in mileage?
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Senior User
Joined: Jan 2009
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From: Midlothian, TX
Significant reduction in mileage?
Just got new cylinder heads and tranny rebuld on 04 5.4 Screw. Have 56k miles. Was getting 17+ mpg before repairs, now getting around 12. Is that normal? Any suggestions? Appreciate it.
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Joined: Sep 2006
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From: New Castle, PA
Winter gas blend definately kills your mileage. I tested with 10% blend and gas with no ethanol in it. I gained a little over 2 mpg with the ethanol free gas. that was with my 4.6 though.
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Joined: Jan 2009
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From: Midlothian, TX
I don't know if we have "winter blend" gas in Texas. We don't have much winter- compared to you guys north of the Red River. I have only put about 100 miles on it since the repairs. My service advisor said its normal during break in 500 - 1000 miles. But that much? Wow. Thank God gas isn't $4.50 anymore.
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Posting Guru
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From: New Castle, PA
Ya, i was getting almost 15 city back in the end of december with non-ethanol gas, and then i reset my computer (had to get a new battery) and it went down 2.5 mpg, but im assuming it will be back up once the computer relearns me. I can already feel it coming around.
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They would have had to disconnect the battery when they worked on truck. That will cause the computer to go back to the factory settings. Check your mileage after a couple of tank fulls. Like xjcamaro89, your mileage should gradually come back.
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Joined: Jul 2008
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I wouldn't totally blame winter blend gas for drop in mileage. Going back to the days of carbs and my drag racing in the 70's, colder air is denser than warm air. These engine management systems used on modern vehicles are so good at maintaining the 14.7 air/fuel ratio that colder air requires more fuel to maintain that A/F ratio and hence a significant drop in MPG. On the occassions where I could only get 10% alchohol blend gas I've only noticed a 1/2 MPG drop all other conditions being equal. In the winter months in northern Indiana I'll lose 1.5 MPG on the my 06 5.4L F-150 as well as my wife's 3.0L 24V Taurus. That also applied to the 95 5.8L F-150 s/c I used to own. After the battery is diconnected for several minutes as happened when Lakefortfisherman had his truck serviced, it does take a tank or two full for the truck to relearn the strategies that were in the PCM before the repairs. I wouldn't panic right away, but I would definately monitor for a couple of tanks of fuel during normal driving and if MPG doesn't improve I'd be back where the work was performed to complain about the fuel mileage.
Greg B
06 5.4L S/C XLT 4X4 stock for now
Greg B
06 5.4L S/C XLT 4X4 stock for now
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