From what I understand that is true. It certainly is the case for my brothers 24 valve truck with a Comp box on it. The overhead reads higher mileage than what he is really getting. Makes you feel good until you do a hand calc and find out that your being lied to. .

 

I Have Had My 2001 For 2 Years Know I Bought It In Texas And Drove It Up Here To Ohio And The Best I Have Ever Got Is 13mpg And It Does Not Seem To Matter How I Drive .

 

I think that the 24 valve uses significantly more fuel after 2000 rpm. You can almost run another 100 miles or so on the same tank if you run it a little slower. I know if I keep mine under 2000 which is really really hard to do I can go almost 2 weeks without getting fuel, on the other hand during Truck Bash and the Dhra weekend I can go about 4-5 days on one tank.

 

just made a trip unloaded to florida and back and i averaged 24.6 MPG with the twins set at 48 PSI and the cruise set at 70-75 nearly the entire time "this was calc by hand not the overhead unit.....but it was far off cause it read 24.9 MPG"

 

That makes me feel a bit better, looks like our trucks are built very similarly.
Except for the twins of course.

 

Just back from a trip from Houston, TX to Phoenix, AZ. 24.9 MPG. No trailer, just the family, and a bunch of stuff in the bed. Set the cruise at 68 MPH most of the time, did not go over 70 very much at all. Stock truck, no mods except muffler removal.

 

WOW Thats great mileage. Did you hand calc it or overhead display?

 

Hand calculated. Overhead reads around 22, but it has always been 'off' ever since I got the truck.

 

I wish I could get better. I need it, Macoroni and cheese is getting old. All my play money now seems to be going into the tank. I have a K&N, and straight piped. Anything else I could do?

 

Corrected 22 mpg highway @ 65-70 mph. 18 mpg in typical driving. Truck is stock other than Magnaflow muffler.

 

Consistenly 22mpg. Took a trip to yellowstone last year and got 29mpg. Drove from Jackson Hole, Wy to Saint George, Ut on a tank and still had some to burn.

 

I get 18.5 round town and 26 on the highway. I checked comp guage against actual (miles/gallons) and it was right on. I'm not sure if it's normal or not.

 

I only get about 14-16 ...

 

Don't How True This Is But I Heard At The Dealer People Complaining That When They Brouht Their Truck In For Service And The Dealer Did A Cummons Update Reflash On The Ecm That Their Mpg Went Down The The Dealer Said Theres No Way They Can Reverse The Reflash. If Anyone Knows More About This Please Fill In.

 

Just did an all interstate 800 mile round trip at 80mph for the majority of the way. 16.6 mpg, not bad for 4.10 gears and 315s.