And, then, maybe your "new" overhead console is bad...

 

I was just gettingg ready to post the truck it came out of has the smaller tank I have the 35gal tank would the dealership be able to program it to make it know I have the 35gal tank

 

Witch could explain the gas mileage as it's thinking it's looking more gas then it really is

 

On that, I don't know...... That would be one for the dealership to answer.

 

So I've been thinking about your DTE problem...

The truck may "know" ( or more likely, thinks it knows) how much fuel it has used but how does it know how or when fuel gas been added. Therefore:

1) there should be a reset button or some other way to let the gauge know that you filled up

Or

2) there should be some kind of sensor in the tank or on the sending unit to tell it how much fuel us in the tank.

I really have not gone into the wiring for this yet but I'll try to soon. Have you checked into it yet?

 

On the newer trucks, I think the gas gauge already goes thru the pcm, before the info gets to the cluster. (98 and up)