Hello everyone, I just went on a road trip to Michigan from Oklahoma. My mileage sucked. I could only get at best 15.5 MPG rest of trip was less. And yes this was using the computer. Now just think the computer is actually 1 MPH better then hand jamming right? So what the heck is going on with this thing!!!! I used 91 fuel or higher and I did have my Pro Comp (hypertech) progam in, left it in O/D and averaged 75 MPH also have the 3.92 LSD. Well I pulled out program and I'm gonna see if the mileage getts better. I head back to OK Sunday without program and check it. Guys I know it's not a KIA, Honda, etc. But this is crap. Love the truck, but this mileage stuff really sucks literally!!!! I've read on here other guys with 4X4, 3.92 rear ends with better mileage. I am so confussed with this thing. Only thing I have done is the K&N drop-in and Mufflex, and now minus programmer and see what gives.

 

Is this truck a 4x4? Fuel mileage can be a fickle thing. So much enters into it. Headwind, tailwind and the wind speed of either of these make for wild swings. Also rain drags down mileage.
You say you averaged 75mph. Does that mean you maintained 75 on cruise or that you averaged 75 mph for the trip. I was assuming you maintained 75 on cruise and that is probably a bit high to expect your top mpg's. If you averaged 75 for the trip you were "hell bent for election" ;-)
If you have a chance to- try slowing down to 60-65 mph and see what happens.
Other than reducing speed I don't know what else to tell you cause you can't do anything about the weather.
It'll be interesting to see how your return trip goes. Good luck.

kasjun

 

65+ in a truck this size kills mileage. I know it is no fun but like kasjun said - cruse at 65 and I bet you see 2mpg better

 

Yes I guess I should have explained better. 75 MPH using cruise control. The speed limit is 70 from OK to Mich. Its wierd though went to Texas and averaged like 17 MPG and speed limit in OK is 75 MPH.

 

I get over 17MPGs with my RC Hemi 4x4 with 3.92s in MI on the puter at 75. Same mods as you minus the programmer.

The cooler weather would have hurt your MPG as well.

 

I notice a pretty big difference if I maintain 65 on a trip vs. 70-75 mph on a trip. I think the fuel saver struggles to kick in over 65 unless you have a nice tail wind.

 

I have been averaging 16 to 17 mpg (4x4 3.55 gears). My mileage dropped since they started using there winter blend to 15.5 16.3 hand calculated. But I also started to drive the truck regularly vs trying to get the best fuel economy. Still better than my 07 Ford F 150 4.6 which averaged 13.5 to 14.5 best all year round.

 

did not know we HAD over drive?????? cruising at 75MPH will kill gas mileage in any car/truck. what is winter blend gas??? winter blend diesel yes.

 

Everything that is said here is true. Just a couple weeks ago I took the 03 from home to near Cincinnati a total of about 125 miles one way. Over half of it is on 70 MPH roads. I typically run right at the speed limit and got 18.9 MPG on the trip up. For the return trip with a warm front coming through and a still southerly wind it brought that all the way down to around 16.5 so it makes a heck of a difference. I was astounded by how much. Also I do notice that cooler weather also brings it down. Check the tire pressure and run as much as you can without adversely affecting the tire wear.

The 09 of mine is a 2WD and with no wind at the speed limit I can get as high as 22 MPG with no wind in warmer weather. Heck I get 14 MPG pulling a 5,000 lb. boat! The biggest piece of advice I can give you on getting good fuel mileage is to stay off the brakes. By that look way far ahead and when you see you may need to slow down or stop take actions early by clicking of the cruise and not using the brakes. When accelerating back up to speed be very easy on the throttle. I generally average at least two MPG better than the wife. She is wide open or full brakes. We get there at the same time! She also drives faster too. We still get there at the same time.

 

75 MPG with 3.92 gears explains a lot.

75 MPG with 3.21 gears gets me 18-20 MPG depending on which way the wind is blowing.