how fast do you drive

Then you have something wrong with your truck. Every truck that I have ever driven or owned has gotten better mileage when I wasn't in a hurry and slowed down.

 

54mph if time allows. last week on a trip from Lenexa KS to Phoenix I got 8.92mpg with my 14L detroit

 

From the looks of your avatar I would say that you should probably be in a hurry.

 

BTW, I do have something wrong with my truck at present. It's been at the dealer for almost a week now.

 

LOL...I love it when someone says something like this...so if I go 80 MPH instead of 60, then its not much of a factor then? How bout 2 MPG of a factor... = around $27000 for the year out the stack. You must be independantly wealthy...

 

50 uphill, only 90 downhill. I don't want to overstress my tires since they are only rated for 75.

My speedo goes up to 120 though. Mpg high 4s - low 8s with stock nozzles but fuel/torque maxed and 198123 Schwitzer. 3406C CAT

 

Do you know the sweet spot for your engine ? Mine is 1400 - 1500 . That's 63 - 69 mph .

 

Reduced window of reaction time, dramatic increase in braking distance and inability withstand the force of a colision resulting in crumpling twisted metal and shattered glass are more a factor at 80 MPH.

 

But the first to the scene of the crash!

 

I have a big truck . I only drive as fast as I can .