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IDI nooby
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Discussion Starter #1
I am driving 125 miles a day for college and I am wondering how I can get better mileage out of my truck. its a 7.3 idi 5 spd with 3.55s I got 235 tires and was wondering if I should stick with these or get some thing different for better mileage. I get about 21 highway.
 

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drive 55 MPH, accelerate slowly, coast into stops for as long as you can while down shifting using the engine to slow you down. 21 MPG ain't bad
 

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Stick with the 235s. It don't get any better for MPG. Air 'em up to the max on the sidewall. I run 100 psi, but I run Firebombs.

Best hardware mod is to clean up your bed. If you can live with a tonneau (hard or soft - no differnce in MPG) get one. For me my tonneau is worth a solid 1.5 MPG over an open bed. Better, but more expensive and time consuming to make is a sloped "aerolid." That's another 1.5.

Forget intakes and exhausts, unless you are going for more power. They don't help MPG.

I posted a link in another thread about changing your driving. "Adjusting the nut behind the wheel." Read that and use what you can.

I started with 18 MPG. You got a good start. Don't underestimate an IDI for MPG.
 

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IDI nooby
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Discussion Starter #5
Oh I know its good mileage, but I cant use a tonneau cus I regularly through crap in the back and I just like to keep my bed open just in case I need to haul a goosneck or anything. I usually accelerate pretty slowly but I go 70-80 mph depending on the rush. My pump is turned up about an 1/8 of a turn I think and Im thinkin bout a diff air intake for a little more power and to clear up some of the smoke.
 

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Air those 235s up rock-hard. These trucks' MPG is very sensitive to under-inflated tires.

I run 100 psi in mine but they are E-rated Firebombs and it is much safer to overinflate Firebombs than underinflate them.
 

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Air those 235s up rock-hard. These trucks' MPG is very sensitive to under-inflated tires.

I run 100 psi in mine but they are E-rated Firebombs and it is much safer to overinflate Firebombs than underinflate them.
What kind of mileage are you getting with your 7.3?
 

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Steady 26 in mixed driving. Have had as high as 28.

Gotta work on my aerodynamics more.

What do you get? Let me guess - - - 14 to 16.
 

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Wow thats pretty good. Highway I took a trip to Maine and almost got 18 with the SRL tune. I also have an extang bed cover that isn't mentioned in my signature.
 

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Most SDs get between 14 & 16. 18 on the highway.

Modifiers:
4x2: +2 MPG
6-speed: +2 MPG
4" slam: +1 MPG
Flat tonneau: +1.5 MPG
Aerolid: +3 MPG (Note aerolid & tonneau are mutually exclusive)
3.08 gears: +2.5 MPG (3.08s are VERY rare 3.31 or 3.55 are available)
GV Overdrive: +2 MPG

You see where my MPG comes from. But then, there is the Dark Side of Modification

Big Tires: - 2 MPG
Lift: - 2 MPG
Gearing: -1.5 MPG (anything over 4.10)
Crew Cab: - 1 MPG (excess weight)

You can see how even diesel trucks can sink to 11 MPG or so.
 

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No. I use an economy tune from Swamp.

Tuning may help an egregious fuel hog but for me gains are small.
 

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What aero mods am I working on?

1. Getting ready to modify my TT mirrors (paddle mirrors have been pulled off and the TTs back on) to allow me to fold them back when I’m not towing a trailer and still be able to see behind me on the sides.
2. An improved “fastback” aerolid. You have to balance reducing drag with maintaining visibility. I’m visualizing 4 or 5 “steps” with a flat aluminum plate as the “tread” and a plexiglass “riser” to see out of. The whole thing slopes down at a ten degree angle. Much like the rear window of a Lamborghini.
3. Fender skirts.
4. Further up the road, a completely new style of bed. In the plan (overhead) view, it would begin tapering back at a ten or twelve degree angle at about the back edge of the tires. That would allow me to reduce the wake area of the truck by 40-50% if I combine that with an improved aerolid. I still maintain a 49” wide cargo area.


Now, if I can just hit the lottery, I can make all this look professional.
 

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Sounds like you got a good amount of work ahead of you. Good luck with everything man. Yeah thats what were all saying right now. Ha
 

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What aero mods am I working on?

1. Getting ready to modify my TT mirrors (paddle mirrors have been pulled off and the TTs back on) to allow me to fold them back when I’m not towing a trailer and still be able to see behind me on the sides.
2. An improved “fastback” aerolid. You have to balance reducing drag with maintaining visibility. I’m visualizing 4 or 5 “steps” with a flat aluminum plate as the “tread” and a plexiglass “riser” to see out of. The whole thing slopes down at a ten degree angle. Much like the rear window of a Lamborghini.
3. Fender skirts.
4. Further up the road, a completely new style of bed. In the plan (overhead) view, it would begin tapering back at a ten or twelve degree angle at about the back edge of the tires. That would allow me to reduce the wake area of the truck by 40-50% if I combine that with an improved aerolid. I still maintain a 49” wide cargo area.


Now, if I can just hit the lottery, I can make all this look professional.
So if i go back to 235 75 r 16 or 265 75 r16 tires and stock height i will get better MPG even with 4.10's????
 

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Yeah...I have factory 373's and the low end just isn't there because of the gearing...I was just trying to see what you would recommend.
 
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