I'm surprised my highway MPG, when unladen, is as high as it is considering the gearing, size of the engine, tires and weight. Is anyone else running this set up? What are you getting with your 6.8L on the highway?

 

I checked by hand one time. 8 mpg with only 4000 miles on my of that 3000with camper in tow. About the same as every other gas.

 

Have you put a tune on it to account for the larger tires to correct the speedo and odometer?
If not, then the MPG calculations will be pretty far off.

 

Yes, I used Forscan to update tire circumference to 2799. I was able to input 29XX just fine but did some empirical testing using GPS speed comparison and GPS distance driven. 2799 was accurate even though that is a smaller circumference than what I actually measured with 37x11.5 Nitto Trail Grapplers.

 

Where do you live? Driving in Kansas or Florida is far different than Utah or West Virginia.

 

What mpg with the stock tires/rims?

 

Thats pretty damn good. Now…. Watch out for the incoming fire. Diesel guys can’t stand hearing a gas set up getting above 10mpg lol. Enjoy your truck.

 

Live in Salt Lake City ~ 4400 ft

 

Still stock rims - I put 37s on the stock wheels and stock suspension. I did a drive from Salt Lake City to Boulder with the stock tires and got 17.0 MPG. Maybe highway is slightly better with the 37s due to lower RPM at 75 MPH.

 

careful now, 37s on 4.3 is equivalent to 32s on 3.73. That's dangerously high gearing around these parts.

 

That is the exact reason 4:88 are clearly the best gear ratio for a gas motor. Thanks for pointing that out.

 

Yet ford doesn't offer it in pickups so all those 7.3 and 6.8 with 4.30s are also going to blow up soon from lugging.

 

How about the 7.3 F450 & F550 Chassis Cabs that come with 4.88’s?

 

Thats pretty crazy high with mud tires. Check your speedo with a GPS such as waze.

 

That is why we have 10 gears. Just pull in 3rd.