Why do some trucks just get poor mpg?

[2dedge]

I know this is a sore subject and I need to remember I have a 9000lb 4x4 excursion but I hear that other trucks do better I typically see 10 towing a 24' enclosed race trailer that weighs 8k or 14 with the truck only.

Then I read threads where even some tuners trucks just don't do well regardless of the tweaks in tuning.

What are we all missing?

I have checked all the wheel bearings, brakes are all free, went back to stock tire size no boost leaks, new uppipes ect. I changed to single shot ac's, van turbo, tuning multiple times ect. Smoke had gone down so I am getting less wasted fuel but the mileage doesn't change?

Doesn't matter if I drive like a grandpa or normal hand calculated numbers are always the same.

On the highway I see 600-700 degrees and 2-4lbs of boost on flat ground.

 

[MossBack]

Fluids... engine, transmission, t-case, front and rear diff's. After I switched all that over on my 1997 i went from 14 combined to 17. And a best highway of 21 mpg's..

 

[TyCorr]

^ that always tapers back off after 5k miles or so for me.

 

[2dedge]

Good thought on fluids

I have
Rottela 15/40
Swepco tranny and t case
75/90 front diff
90/140? Rear diff

 

[MossBack]

Good thought on fluids

I have
Rottela 15/40
Swepco tranny and t case
75/90 front diff
90/140? Rear diff

If you daily drive and tow under 10k it is ok to run 75/90 front and rear. I think that helped raise the MPG's the most .

And like I said I run full synthetic severe gear AMSOIL

At a minimum get a name brand synthetic. Even though AMSOIL might be cheaper then you think....

 

[Crack85]

Please refer to here. It answers all your questions:

http://powerstrokearmy.com/forums/showthread.php?t=17133&highlight=Tank+250+gas+mileage

 

[POWER-STRUCK]

If you daily drive and tow under 10k it is ok to run 75/90 front and rear. I think that helped raise the MPG's the most .

And like I said I run full synthetic severe gear AMSOIL

At a minimum get a name brand synthetic. Even though AMSOIL might be cheaper then you think....

^^^^^^^^^^what he said^^^^^^^^^^ sometimes we just need to ignore the price of some things, get past our overly conservative ways to "get the good stuff" sometimes we need to "buy the good stuff" fluids are the life of anything that goes vroooom. you can spend some money now or spend alot later. if you figure dollars per mile you will come to the conclusion that the fluids pay you to run them! others that have unexplained low fuel econ might need a mirror to find the problem!

 

[jaybuller]

I think the biggest differences in mpg will be the drive and terrain...second biggest will be the condition of the wheel bearings, brake(dragging) hydro brake rusted inside hanging brakes, and then tires...both size and design.