Can anyone tell me the approximate mileage I should be seeing with my 7.3. It is a F-350 with an automatic and I am running 35's. I have the edge programmer and 4" exhaust and have done the transmission. I usually see 10 to 12 mpg. Does that seem normal?

 

What are you using for your mileage estimates? If you are relying on the overhead display, forget about it. Once you put a chip or programmer on it, then it's no longer accurate.

If you are hand calculating the mileage, then there are two things you have to account for.
- First is your tire size. You need to find out if your speedo is accurate, and if not, it needs to be re-calibrated. Otherwise, all of your hand calculations will be off (and lower than they should be) since you drove more miles than what is indicated on the odometer.
-The second thing to consider is how much fuel you actually put in your tank. The stock fuel tank has a vent tube that sticks several inches inside the tank. The problem with this vent tube is that it causes the diesel fuel to foam during fillup. When the pump automattically clicks off, your tank isn't really full. If you have the patience, you can dribble in an additional 3 to 8 gallons of additional fuel before it's competely full. This discrepancy will cause mileage calculations to be innacurate between each tank.

For your truck, expect 14-16 mix driving. To increase fuel mileage, keep RPM's below 2000, and drive like there is an egg between your foot and the pedal.

Also, winter mileage is worse than summer. The winter blend fuel is to blame, as well as any extended warmup times, and the exhaust backpressure valve operation.

 

Agree with Pocket.

I also have a F350 7.3L, 35's and auto, 4" exhaust, programmer, Crew, Long.
Empty I see....

Winter: Stop and Go commuting = 14.5 mpg
Summer: Stop and Go commuting = 16.5

Winter Highway = 17+ mpg
Summer Highway = 19+ mph

You may want to clean out our EBV if you havnt recently and I bet it goes up!

 

Dang i never knew that the vent tube caused that much of a difference.

And that milage seems low im getting anywhere between 11-14mpg and im running 38's

 

I had checked the odometer on I-5 in one of the states odometer check sections. I found that mine was off by .1 miles every mile driven so when I calculate my mileage I add ten miles to every 100 driven. With that I still end up with what seems to me low mpg. I haven't cleaned the ebv, but I will soon and let you know if that helps. Thanks for your input!