But maybe your truck does get it, can you tell me what im doing wrong? What can I do or buy to improve mileage? My truck has a new fuel pump, filter, air filter and complete tune-up all no more then 8k miles.
Without riding in your truck or watching you drive there is little I can offer you past what I have already mentioned.
My 97 Tahoe was a 4 dr 4x4 with 3.42's. It was 100% bone stock. It was in good tune up. Washed and waxed weekly. 16 city/ 19 hwy was no issue.
Things to consider are climate and altitude where you live. I moved to PA, and even after my truck adjusted to the difference in altitude it never seemed to do the same. But, there was far more city driving in PA then there is for me here in TN, so you have to account for that as well. Roads here are curvy, but no where near so as they were in PA. In fact, comparing the 2, the roads seem straight here. So even the roads can come into play.
I have heard that the road surface can have an effect on your mileage just like the tread pattern of your tires. I have never tried to verify that. Most road surfaces here are the asphalt made with old car tires, and the roads in PA were concrete. I would think the concrete would be the better of the 2 but who knows.
I would recommend going through the wheel bearings and such. Make sure they are all in good condition and not dragging.
Are you running an all season street tire, passenger or a LT truck tire.
Have you seafoamed the truck recently.
Are the plugs properly gapped?
What weight oil are you running? Yes, it really does matter.
Have you cleaned your MAF recently?
What condition are to catalytic convertors in?
What condition is the rest of the exhuast?
What condition is your fan clutch in?
Does your a/c compressor, P/S pump, or ALT have excessive drag due to wear?
When was your alignment done last?
What condition is your steering components?
Do your brakes drag any if you free spin the wheels when the truck is lifted of the ground?
What temp thermostat are you running?
WHAT IS THE CONDITION OF YOUR IGNITION COIL?
What dead weight are carrying around with you?
Little things add up. One or two things might only add up to .05 MPG, but multiple things can really add up.
My 97 was in superb shape all over. The guy I got it from worked in a performance shop and had gone through it for good measure and replaced virtually every normal maintenance item any one would normally go through. I gave it a tune up, and changed the oil. I owned it for 6 months and put 14,000 miles on it during that time. I had plenty of interstate time in it and religiously checked my mileage.