The truck in my sig is my daily ride, a year ago I was going 450 miles and refueling and only using 25 gallons. And now I can't even get my mpg over 14.0mpg no matter what I do I drove about 300miles this weekend and no rise and that's at 65-68 cruise on and running empty.... My lift pump is just at a year old the injection pump is right at two years, I drive easy no hard driving and hasn't towed anything in quite awhile. But this fuel mileage is driving me crazy. So any and all thoughts and ideas would be great I need help!!!

 

try cleaning you map and IAT sensors if that dont help replace them.

 

I cleaned iat and I'm not sure how to get the electric plug offthe map or what size or anything the map is. And another thing to add is the performance hasn't seemed to change in the truck unless it's been so gradual that I haven't been able to tell idk

 

Winter fuel with high mix of #1 diesel and anti gel additives are probablly killing you. Also the USLD fuel seems to have fewer BTu's of heat engery than old LSD fuels. Milage should improve as winter blend phased out for summer blends.

 

I would consider some fueling mods. I'm sure the cold weather is hurting your efficiency, but your mods are very similar to what mine were at one point, and when I added sticks, I got an extra 1.5 to 2mpg and was able to keep my rpm's lower.

A EZ would probably be a better bet, though since it will give you more low rpm fueling, AND some timing. I bet you'd get more than I got from my sticks. I only recently added the chip, and haven't done any efficiency calculations yet. I expect a small increase-but only from the timing.

Fuel filter dirty maybe, too?