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Old 06-30-2010, 06:25 PM   #34 (permalink)
TheEnemy
The road not so traveled
 
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Join Date: Jan 2010
Location: New Mexico
Posts: 680

The Truck - '99 Nissan Frontier xe
90 day: 25.74 mpg (US)

The Ugly Duck - '84 Jeep CJ7 Rock crawler
Thanks: 18
Thanked 66 Times in 57 Posts
Quote:
Originally Posted by Old Tele man View Post
...here's an equation for vehicles in the 3,000-lb. range, attributed to Detroit, that's used to estimate weight changes upon fuel economy:

(MPG2 / MPG1) = (WT1 / WT2)^(0.72)

...where: suffix-"1" is old and suffix-"2" is new.
MPG2 = MPG1*(WT1/WT2)^(0.72)

MPG2 = 26*(3000/4000)^(0.72) = 21

Not even close to what I observed. If I had dropped below 24mpg I would have to get gas at both ends of the trip. Only once did I have to get gas midway in the trip, and that was when I had beds hanging out the sides and over the top.
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