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Discussion Starter #1
New to Diesels but the 6.7 seems to be sensitive to weather changes. I have not hand calculated but the overhead mpg seems to go up the warmer the weather gets, as much as 3 mpg around town during the day @ 50-60 deg and drops at night (still getting into the 30's here). I've messed with resetting overhead the last week or so when I started noticing. Anybody else notice this?
 

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My truck gets better MPG when it gets warmer even when I still have some winter fuel left over. I see my peak MPG gain when the temp is in the mid 70's and I'm running summer fuel again.
 

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Ive herd when it gets cold it gets harder to move the oil around making the truck work a little bit harder. I notice a mileage drop in all my cars when it gets cold. Not much but a little.
 

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Discussion Starter #4
My truck gets better MPG when it gets warmer even when I still have some winter fuel left over. I see my peak MPG gain when the temp is in the mid 70's and I'm running summer fuel again.
I Didn't think of that. Summer fuel vs Winter fuel that may account for some of the difference. But literally day and night differences. Days, warmer, MPG up. Nights cold, MPG, down.
Thanks.
 

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New to Diesels but the 6.7 seems to be sensitive to weather changes. I have not hand calculated but the overhead mpg seems to go up the warmer the weather gets, as much as 3 mpg around town during the day @ 50-60 deg and drops at night (still getting into the 30's here). I've messed with resetting overhead the last week or so when I started noticing. Anybody else notice this?
The warmer the air temp, the less dense the air becomes.

Dense air = more power = mileage -

Less dense air = less power = mileage +

Hope this explanes it some what in short terms. :beer
 

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Also, these ain't the most aerodynamic shapes ever invented.

More dense air = more resistance.
 

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I bet if you hand calculate your mileages, you might be surprized at what its doing, or actually ain't doing. I have seen as much of a 3 mpg increase in the OHC and when I run the numbers by hand its not gone up at all... I have yet to figure out what the OHC is doing and how it gets what for the readings, but that is one screwed up guage if you ask me.

This has been what I have seen with mine anyway. Yours may be different. I do know there is a flash to get the OHC better calibrated and I plan to take the chance and have mine reflashed yet again one of these days when I have the time and my tech can get me in...

All I am saying though is don't lay much faith in the OHC reading until you run the numbers for a few 1000 miles to know for sure. Heck I can't even trust mine to show what settings work best on the juice and how I set up the low end response on the juice. My OHC just doesn't track linear with what the mpg should be doing at any one time...
 

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Discussion Starter #8
All I am saying though is don't lay much faith in the OHC reading until you run the numbers for a few 1000 miles to know for sure. .
Your probobly right, mine won't even show the right tempature sometimes. Gets stuck on 67deg even in sub zero weather. Dealer said to bring it in when it is actually malfunctioning. Like thats all I got to do.
 
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