15 I was averaging around 80 on the highway. I'm sure I could get better if I slowed down but it's hard to go that slow 18.1 is fuggin' amazing!

 

the key is to slow down and set the cruise to do 55 and you get over 20 mpg thats how I got 23 mpg on a 300+ mile trip from cincinnati to columbus and back, most of it was highway but 15% of the miles were city

 

not to derail the thread, but were there two different tank sizes available on these trucks and how do i go about finding out what i have?

 

the two tanks are very different in size, like 27 and 35 or something like that, so just run it down till the light comes on and fill it all the way up... if its like 25, then you have the smaller one...

 

Or just look underneath the truck

Or call your dealership and have them run the vin through "oasis" to find all of the factory options on the truck

 

I am pretty sure it is 30 and 35 or 36

 

I just walked in the door from a 450mile trip. MPG 16.2

98% highway.

4.10 gears, 28.5" tires and a blower.

I'm happy with that.

 

you cando way better than that if you slowed down

 

You're right... The speedo was set at 79 mph the entire time.

 

all stock doing 15mpg city and 18.2 highway, driving with light throttle and rarely breaking 2000rpm unless passing someone.

 

next time you take a long trip like that set it at 55 and snail it in the slow lane... you coulda saved yourself 30 bucks worth of gas

 

I used to do that... but my truck will kick itself into fail safe mode if I try to cruize slow.

It's under "no load" and it just freaks my POS out.

 

are you serious? sounds like a tune issue, time for more custom tunes then

 

I'm back the the tune that came with the supercharger. I ran this one for about 10 months trouble free and my only real issue was the way it shifted.

I've tried 2 other tuners and they both didnt know anything about these trucks and neither could replicate the power I'm getting with the stock supercharger tune.

Somthing mechanical or a sensor has just flat out failed and I can't seem to track it down.