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It depends on a LOT of things, but figure around 25-ish?

I don't think you could hit 30 MPG unless you drove it 40 mph and geared it right
 

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Navigator is built off of a 250 SD chassis, not suspension though. I would say if you got everything hooked up, low twentys. Wind resistance and weight are against you. I have yet to meet anyone who routinely gets 30-35 mpg.

Still much better than the 4.6, 5.4
 

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I think the powerstroke Excursions get around 20
 

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hardly.. The powerstrokes and that massive truck gets mid teens, high if you keep your foor out of it. I think a Navigator would be slightly underpowered and get high teens/low 20s max also...
 

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Discussion Starter · #7 ·
from what I have found curb weight is 5970 on the navigator and it is on the f150 chassis instead of the super duty chassis. My 99 super duty weighs almost 8k with a 7.3 it gets 16 and has seen 19mpg before but not often. I have a 97 powerstoke also and with no spare tire, and me out of it it weighs 6500 at the local scrap yard and it gets a consistent 17.2 mpg with 4.10 gears and a manual.
 

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from what I have found curb weight is 5970 on the navigator and it is on the f150 chassis instead of the super duty chassis. My 99 super duty weighs almost 8k with a 7.3 it gets 16 and has seen 19mpg before but not often. I have a 97 powerstoke also and with no spare tire, and me out of it it weighs 6500 at the local scrap yard and it gets a consistent 17.2 mpg with 4.10 gears and a manual.
4BT's rarely get over 25mpg in vehicles that large due to weight & wind resistance. The reportedly "high mpg" (upper 20's & low 30's) rigs tend to be 4500lbs or less, 2wd w/5 speeds & road gears. 20-25mpg would be a good estimate in that particular application which would be nearly a 40% improvement over a 5.4L that might average 12-15mpg
 
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