I used to get 15-15.5 in the summer before the 1714, then with the 91+ tune in the winter it plummeted to 13-ish. The 87 tune is back on, but the PCM has yet to learn my new habbits. I'm over 13 though... and easier on the gas thanks to the sissy tune.

 

Well, I took a 425 mile drive this Saturday. The first half of the drive I tried to drive a consistant 80 miles per hour. At 80 miles per hour I was getting 16.9 mpg. I dropped it down to 70 miles per hour and I was getting 17.4 mpg. So in theory for every 5 miles per hour in overdrive with my 3.55 gears and my 5.4 litre engine, at 55 miles per hour I should be getting 19 miles per gallon...

Wouldn't that be nice if my theory was correct. The only problem with that is if you drive like that in Texas, you'll get driven off a bridge or pushed off the road into a cow

 

My SCREW XLT will get the same sort of mpg if I was doing 55/60 down here in Florida. problem is i usually do 80 or so and I can only get around 16mpg. Load in the bed doesnt seem to make any differance. Towing does !

 

NFW! You must not have filled it up as much the 2nd tank-full. Check the next tank and add the two together: 125.4 + xxx.x / 5.2+x.x = the truth. Please let us know.

 

2005 STX 4X2

Two road trips at 70 - 80 mph

17.25-ish each tank

I'm told by my brother-trucker that's good value.

 

I drove my 04 5.4 w/3.73 4X4 360 miles at exactly 65 MPH and averaged 19.1. A couple of mountains but mostly level so I thought it did pretty well.

 

I recently drove from Houston, Tx to Auburn, Al. According to the GPS it was a distance of 693 miles. I was averaging 73.2mph. My calculated mpg was 18.981 this with a 2 1/2" front leveling kit, tailgate up, and the A/C on.

Ox