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Fuel mileage didn't change on the performance tune but I get a little better with the economy tune. But not more than 1 to 1.5 mpg.
 

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KD7LAG,

Did the power loss and mileage happen exactly when you changed tire sizes? Have you checked your intercooler hoses to make sure that they are fully seated and the clamps are tight? If the idle is still good, but you have suddenly lost power and MPG, I would suspect the intercooler hoses may be leaking causing a loss of boost.
 

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Discussion Starter #23
[ QUOTE ]
KD7LAG,

Did the power loss and mileage happen exactly when you changed tire sizes? Have you checked your intercooler hoses to make sure that they are fully seated and the clamps are tight? If the idle is still good, but you have suddenly lost power and MPG, I would suspect the intercooler hoses may be leaking causing a loss of boost.

[/ QUOTE ]


Yes. In fact the intercooler hose was just replaced about 6 months ago. It wore through (REALLY like those Ford spring clamps) and when the dealer replaced the hose they used the wrong one. Took it to a different dealer and got it fixed RIGHT! That was in May. Yes the milage and power loss was immediate upon installation of the 285's. I appreciate the input, though. /ubbthreads/images/graemlins/warmsmile.gif
 

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[ QUOTE ]
Yes the milage and power loss was immediate upon installation of the 285's.

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That doesn't make a lot of sense to me. I put 285's on my Excursion and it didn't make really any difference in power or MPG. I can boil the rear tires through 1-2 gear with the SC tuner. Without I can still get them going through 1st pretty well.

MPG is 12-14 around town and 16-19 on the HWY depending on all the factors, A/C or not, which SC tune (I actually think I lost 1.5 to 2 MPG around town with Tow tunr over HP tune) speed etc.

FYI, I never did get the rev's per mile changed either. Speedo is right on according to GPS.

Did anything alse change? In reality, your MPG according to your overhead should have started "showing" lower MPG becasue you're now covering more ground than you speedo/odo says you are becasue of the 1/2" or so taller tire. Mine is almost always right on compared to hand calc. MPG.
 

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Discussion Starter #25
You know what?!?!? You're right. I never "did the math". Just went by the OHC. I told you I wasn't the sharpest knife in the drawer. BUT the percieved power loss is real. I did drop my ability to pull the 5th wheel up a steep grade like I used to. I will start doing manual checking on the MPG on my next tank. Thanks for the heads up (no pun intended). /ubbthreads/images/graemlins/warmsmile.gif
 
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