MPG - 12.5: is it normal?

[kapinallinen2]

I get 14mpg if I go 80 on the highway. I'm not so sure it's about aerodynamics.... I have 3.92s

I get 12.5 to 13.5 mpg at 80. Drops down to 10 mpg with the RTT sticking up a foot above the roof line.
I saw a video on YT. someone went WOT at the limiter, getting about 4 mpg. IIRC.

 

[Darksteel165]

I get 12.5 to 13.5 mpg at 80. Drops down to 10 mpg with the RTT sticking up a foot above the roof line.
I saw a video on YT. someone went WOT at the limiter, getting about 4 mpg. IIRC.

Yep? I was just responding to the person that gets 19-20mpg at 80 mpg.
Also you can't be WOT at the limiter, that's an oxymoron. When you hit the limiter the engine reduces power and ignores your foot on the peddle for a few seconds.
Acceleration has nothing to do about mpg vs constant speed, obviously accelerating you will get bad mpg because you are using your engine to do more then coast.

 

[23RAM]

I've found most vehicles are tuned for economy around 68 mph. It's not just drag and aerodynamics, it's also engine rpm and over a specific rpm the variable valve timing changes and opens up the intakes longer which consumes more fuel and produces more power. Listen to the sound of the engine as the revs go up and you'll hear a definite change in engine sound. This is easier to hear if you can lock the tranny into a gear (like 4th or 5th in the city) and then speed up and down while listening to the engine and watching the revs.

 

[theblet]

If you compare these trucks to a Honda accord, they arent very aerodynamic. It takes more power to push the big front end through the air than a light car. This effect compounds the faster you go, because the wind resistance is greater with speed. So it will take more power/rpm to maintain a higher speed, than a lower speed.

 

[Trooper4]

Yep, these trucks have a sharp drop off on highway mileage based on speed. I get about 23mpg if I stay between 65-70, 20-21 cruising at 75, and 19-20 near 80. Limited w/ 3.21 + eHemi

18mpg at 85 seems about right...

I get about 20/25 at 60/65, with the 5.7 E-T and 3.92's. It drops fast from there up. Every truck is different. Some good, some not so much. It's a brick, and shaped like a brick.

 

[theblet]

It’s amazing how much a strong wind can affect it also

 

[kapinallinen2]

Yep? I was just responding to the person that gets 19-20mpg at 80 mpg.
Also you can't be WOT at the limiter, that's an oxymoron. When you hit the limiter the engine reduces power and ignores your foot on the peddle for a few seconds.
Acceleration has nothing to do about mpg vs constant speed, obviously accelerating you will get bad mpg because you are using your engine to do more then coast.

Let me re-word that. "Went pedal to the metal" Was 2 mpg under full acceleration and 4 mpg at the governed top speed.