19mpg at 80mph? Better hold on to that one, cause it's one of a kind. I get about 15mpg in my extended cab short bed auto 4x4, and that's at 75mph. If I drop down to 70 or 65, I might get 15.5.

 

I never managed to break 18mpg out of my 6.0. I averaged 16-18mpg unless towing then it was anywhere from 10-15mpg. Keep in mind mine was a ZF6.

 

Its always done me right! My wife was driving it home to Florida from Ohio and she said the fuel computer was reading 517 until empty. (of course it could be lieing?)im the second owner and when i got it with 40K on it from a local ford dealer that took it in on trade from an old man, it had a clean oasis report. ((back when diesel was hitting almost $5 a gal)) We bought and have had only one issue @ 135k the FICM took a crap so i had the same dealer install a new one and away she went!

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Whats a ZF6? Im a ford nut thats has converted to Diesel...

 

the manual tranny in the super duty's

 

That makes more sense. The computer in the truck that reads mileage, that's often referred to as the "lie-o-meter" if you really want to check mileage, fill up to the top of the next with fuel... not when the pump kicks off, you must keep going until you have diesel in the neck. Then run it down, record mileage, and refill the same way.

 

Amen brother. The trip computer is a mild suggestion. Once you figure your real mileage, you can use that number as an indicator of up or down. I never got better than 17 mpg brand new and was down below 15 by breakin. Was down to 12.5/13 and blowing heavy black on acceleration. I now have 144K, an edge tuner, air raid intake and 4" exhaust with egr delete. 16.1 if I baby it, but getting 14.5 driving like a BOH on tow package. Hauls a 31 ft airstream like its not even there.