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Jack Ken
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215 Posts
Discussion Starter #1
I took a short trip this week and reset the ol lie o meter and was wathing it in the Ex. When I was at a steady 57ish the meter was reading 20.5. When I sped up on the interstate to 68ish it dropped to 16.5. Now Im not saying these are 100% accurate but with my chip on and then the speedo not recalibrated for the bigger tires it has been farily close to actual mpg. Anyone else notice that BIG of a change in that 10mph? Cause thats HUGE! I knew it would be less but never thought that much. Has anyone done an actual test at a constat 55-60 on a whole tank on a lifted truck to see if my meter is close?
 

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I know on the cars i have had with lie o meters best feul milage was had at about 55 if you wanted to drive that slow. At 70 it would go down a mile or two per gallon and at 75 it would go down another mile or two. So i can defianately see that happening especially with lift and 35's. Wind also makes a bigger differance than most people think so if you were going into a head wind that could of exagerated it.
 

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Increasing your speed from 57 to 68 (a 19% increase) increases aero drag HP by 70%.

Aero HP increases with the cube of speed.
 

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Jack Ken
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215 Posts
Discussion Starter #4
So it sounds like the ol lie o meter was fairly consistant then. Now if I could only convince the wife to leave for work 2 minutes sooner our mpg average should go form 13 to around 14 or more... at 4 dollar fuel adds up fast.
 

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Fordman, I have done the same thing in my Ex. If I can tuck behind a big rig down the freeway the best I have seen on the lie o meeter is 22.5 mpg with my stock wheels and tires. With my 285/75R16's the best is 20. I have not hand calculated a tank from doing this, but i have hand calculated other trips and the lie o meter is pretty darn accurate in my truck.
 
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