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I've been keeping track of my mileage religiously since I first bought my 2004 Excursion 6.0, both on paper and now with a phone app. Over the course of my ownership, I've averaged about 16MPG both hwy and city. I know that my hwy average is based on my speed, but when I do about 72MPH, I get around 17.5MPG. When towing my trailer (about 7,000lbs or so) I get 12.5 while doing 65MPH.

So here's what's baffling to me. I had to make a trip this weekend pulling the trailer part way and then continuing, and eventually going back to get the trailer. Total mileage was 420. I pulled the trailer 140 miles doing about 65MPH. I drove without the trailer, at 82MPH for 140 miles. I drove back to the trailer, 140 miles, at 70 MPH. I fueled up before picking up the trailer and heading home. Average mileage for the trip was 15.25MPG. The whole way was full of hills, so it's not like I had a lot of downhill. Plus, the pulling and 82MPH should have absolutely killed my mileage. I don't get it. Do you think I just had a hell of a lucky day and the wind happened to be with me at the right times? lol
 

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Wind could do it. I like to keep an eye on tall grass and flags to let me know what the wind's doing on a trip. The wind can easily switch on you at any time, and it can make a big difference in fuel use.
 

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I consistently got 17 to 18 mpg on the highway in my '05 Ex with the 6.0, and that was at 80mph. Above poster is correct, wind direction is paramount while driving a box down the road. Although I never investigated it, I was always curious about what the drag coefficient was.
 

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Discussion Starter #4
I consistently got 17 to 18 mpg on the highway in my '05 Ex with the 6.0, and that was at 80mph. Above poster is correct, wind direction is paramount while driving a box down the road. Although I never investigated it, I was always curious about what the drag coefficient was.
I WISH I could get that mileage at that speed! I get 18-19 doing 72, but when I hit 80 it goes down to 15 very quickly....and that's with neutral wind. Around here, the wind is usually blowing about 15-20. I know wind at your back can help, wind at the nose hurts, but my numbers were just odd for me.
 

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On a long trip, I saw a 3 mpg increase changing the speed from 70mph to 80mph.

At 70mph I observed only one or two psi of boost but at 80mph the boost had increased to about 4 psi.
 

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On a long trip, I saw a 3 mpg increase changing the speed from 70mph to 80mph.

At 70mph I observed only one or two psi of boost but at 80mph the boost had increased to about 4 psi.
An increase by increasing speed??
 

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I'm sure he's saying that his mileage increased at 70 mph compared with 80.

His boost tells the same story, 1 or 2 psi at 70 mph vs 4 at 80. The engine has to work harder at higher speeds to push more air out of the way and accommodate the increasing friction in the engine and tires, etc.

It's all pretty linear: the faster you go, the more you pay.
 

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I'm sure he's saying that his mileage increased at 70 mph compared with 80.

His boost tells the same story, 1 or 2 psi at 70 mph vs 4 at 80. The engine has to work harder at higher speeds to push more air out of the way and accommodate the increasing friction in the engine and tires, etc.

It's all pretty linear: the faster you go, the more you pay.
Apologies for the slow response...

Yes, my MPG went up! I know y'all don't believe it. And had I not hand calculated the mileage myself, I too would be skeptical.

Road trip from Dallas, TX to Tucson, AZ. Same "fill each tank until it won't take a drop more" process for every fill. No changes in tires, pressure, or dropped off a trailer. In fact, we added one passenger on the way back.

I had read that the RPMs being higher than 2,000 was a MPG killer, so I ran 70 MPH everywhere I could.

My sister flew into Tucson and we spent a few days with Dad, then she rode back with us.

On the return trip she took the first driving duty. Her knowing nothing about the 70mph protocol, she wound up the truck to the 80 mph speed limit. Before I said anything I checked the boost gauge and noted the higher reading, and then said nothing.

I fill everytime I stop. And with 3 girls in the truck, we rarely get into the 'danger zone' of being low on fuel.

I eagerly calculated the mileage at the first stop...19.7. Next stop, 19.9. It was consistently 19.8 and 19.9.

Never hit an honest 20. But, it was a definite MPG improvement, believe it or not.
 

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Were you following a semi? Got that drag action going on? Downhill driving will do it and, yes, a difference of only 5mph will do it to when you're at 65 to 75.
 
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