gas mpg problem
08-06-2006, 10:03 PM
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gas mpg problem
Ok guys I just came back from a 500 mile trip with my dad. Same truck, bought it the same weekend, very close total miles. We cruised at about 65. He averaged 22.4 mpg and I averaged 11 straight up. The differences we have is he has stock tires and I have 35x12.50 mud grapplers. He has a weld on magnaflow muffler and I has straight pipe. Now Is that increase in tire size hurting me 11 mpg? this sucks.
08-07-2006, 07:48 PM
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bump, little help guys? Will that tire increase hurt me 11 mpg? Or is it because I have a straight pipe and he has a high flow muffler. Someone told me that a straight pipe (no muff) actually hurts mpg because these trucks need alittle back pressure with the varible geometry turbo.
08-07-2006, 08:19 PM
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Both hand calculated and did ya watch your dad filler up before and after....sounds like your dad is smarter than a fox. I drove my truck for 500 miles as fast as I could 82mph... rolling average.....122 maximum.....several times....through Pa and NY and Mass big hills.....14.5 mpg hand calculated....I was hoping the overhead was right...it said 20.5 .ks
08-07-2006, 08:21 PM
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M/T's have a lot more wind resistance on the hwy, especially wide ones. I was running some 315's AT's then went back to 285's for better mpg. I doubt there should be 11 mpg difference though.
08-07-2006, 08:27 PM
#5
I think I have it figued out. You can't run GAS in that truck! 
Seriosuly though, those tires eat up some fuel, lots more weight to spin & road resistance. I doubt the stright pipe has much if anything to do with it.
Seriosuly though, those tires eat up some fuel, lots more weight to spin & road resistance. I doubt the stright pipe has much if anything to do with it.
08-07-2006, 08:44 PM
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is that hand calc milage? or overhead? did you get the speedo recalabrated for the 35's?
fyi: i threw 35" toyo's on my truck and average economy hasnt changed. in town is lower, but hwy is better, it just averages out with as much traffic as i drive in. my overhead now reads 17.3 but hand cal is over 20 still..
then again on the rare ocation when the wife drives it, the average drops a bit... mayby your dad's a better diver than you...
fyi: i threw 35" toyo's on my truck and average economy hasnt changed. in town is lower, but hwy is better, it just averages out with as much traffic as i drive in. my overhead now reads 17.3 but hand cal is over 20 still..
then again on the rare ocation when the wife drives it, the average drops a bit... mayby your dad's a better diver than you...
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08-07-2006, 09:30 PM
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yes I did watch us both fill up, we were driving on open roads most of the way to Reno, Nevada from CA. The majority of the time we were both on cruise control. Also It was hand calculated and I included the % difference from the tires to the mpg. He might drive better, but I doubt 11 mpg better. Maybe I need to re-gear. Both our trucks are have 3.73
08-07-2006, 11:23 PM
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blackdodge don't forget that your speedo is off with taller tires and there for so is the odometer. i also run 35's and i'm really considering going to the 4.30 gear because my mpg is horrible in the city mostly. re-gearing i doubt will help hwy mpg though.
08-08-2006, 08:15 PM
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Originally Posted by BLACKDODOGE
roc155 what is your mpg? I know my OD is jacked up and I also know that after 450 miles my dad had over a 1/4 tank left and I'd already filled up and some.
08-08-2006, 08:35 PM
#13
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Originally Posted by BLACKDODOGE
\ Someone told me that a straight pipe (no muff) actually hurts mpg because these trucks need alittle back pressure with the varible geometry turbo.
I dont know if a straight pipe would hurt a VGT or not, either way the first VGT available on a Cummins (in a Dodge) will be the new 6.7 for 2007.
