This weekend I took a 200 mile trip to ride 4wheelers and pulled a trailer with just a rhino on it and a honda in the bed with the programmer on perfomance/tow. I burnt three quarters of my tank. Best as i can quess is about 10 to 11 mpg. Trucks runs good and no missing. What in the world is going on. It was not cold and I did not hot rod. This truck averaged 16 mpg last week when I took a trip that was interstate and some in city. And that was with the programmer on high. The programmer is superchips. I have kn cold air 4in exhaust. from what Ive read about this truck it should be way better than what is getting. Im running 33in tires. OH, this is a 2002 with 165000 miles four door 4x4. I changed the fuel filter about 5000 miles ago. Any suggestions? Thanks

Pull out the dipstick and check oil level. An injector failure will have flooded the crankcase causing oil level to be extremely high.
Wags

Clean MAF with Electrical Contact Cleaner.

Good question mine is down to about 13 to 13.5. Thought I had a fluke last tank got 15!! Was doing around 17 4 months ago.

is it possible the gas stations have switched to winter fuel, causing your decline in milage?

I really think it is this crappy ULSD. There seems to be alot of posts on here about drop in fuel mileage since gas stations have switched to the ultra low sulfur diesel. My fuel mileage has dropped abut 2.5 miles per gallon. My boss has a blue oval diesel and he says his fuel mileage has dropped considerably too.

You have an indicator on the engine air filter box, that will show if the air filter is starting to plug, mine indicated a 20% dirty filter, which was enough to change my fuel milage. yet I had blown it out with the air hose, obviously that doesnt work.

good luck drive safe

Anybody that uses the gauges on the dash to guess MPG is wasting thier time. Go to the pump and fill it up then figure the mileage. The GM gauges are a waste of accuracy.

how is your oil pressure?
mine dropped by like half. When I noticed that oil pressure was at 30psi on the highway (and I did right away cuz I lost power right away), I pulled off on the side of the road and towed it to dealer.

is it possible the gas stations have switched to winter fuel, causing your decline in milage?

I am averaging in Summer time about 16-17mpg, winter drops down to 12-14 mpg. Temps and Diesel Fuel #2 (winter diesel fuel) are factors to loose mileage...:mad:

my millage has droped a lot in the past few months. i am only getting 12mpg CITY RIGHT NOW. i used to get 14-15 city.

I am averaging in Summer time about 16-17mpg, winter drops down to 12-14 mpg. Temps and Diesel Fuel #2 (winter diesel fuel) are factors to loose mileage...:mad:
I dont know wether or not #2 diesal has changed at the pump.. But I have switched to winter additive. And that my engine really doesnt have time to get warm before I get to work. Im sure that hurts mpg. But Im like tou, my truck was getting 17 19 in summer.

I don't think you can blame mileage on ULSD. I am still getting 18mpg on ULSD. Both before I installed my Edge box and after. As for getting better mileage on a higher setting for your programmer, that is not all that uncommon. I have heard the same thing from a few other people. Now I leave mine on the third setting and go. I still have stock everything else in the truck...exhaust, intake...I am even using a AC Delco air filter. Speaking of filters, even when mine was showing 80% blockage, I was still getting 18mpg (hand calculated with a mix of city and highway driving).

What could be wrong with the topic starters truck...well, if you are keeping up on your fuel filter. I am sure your air filter is receiving the same attention. You never mentioned what speed you were traveling at (actually RPM is more telltale than speed). Keeping RPMs below 2k does help. The other thing that can hurt your mileage while towing is low tire pressure on you trailer (most forget about those extra wheels until they are flat), along with head winds. Driving into a strong wind can knock 5 mpg off quick!!

i don't think you can blame mileage on ulsd. I am still getting 18mpg on ulsd. x2