01 Sierra 2500 4x4 /4dr Ext Cab/86k - Fuel Economy Sucks!!!!
 

:confused: Any suggestions would be helpful. Truck currently has 86,000 miles and I'm getting ready to replace fuel filter for the second time. I've used several different fuel system cleaners over the last couple of years, installing them at approximately every oil change(6,000 miles) and have been using fully synthetic oil for the last 3-4 yrs. I keep up on all basic maintenence and have yet to recieve any codes. The truck is still fully stock and tires are only slightly larger then the ones the trk came with. I have to research it, but I believe I was getting something like 300 miles to a tank when the trk was brand new. Now I'm lucky if I can squeeze out 240...

What size motor?

motor is vortec 6000 / also changed the air filter and plugs were checked all ok.....

Well I think average on those trucks with that motor is about 16 hwy 12 city. I could be wrong though.

did you change spark plugs it might help I would use Ac delco plugs

I was thinking about doing the plugs and the more people I speak with say this may indeed help. The factory insists these are 100,000 mile plugs n wires , but i'm not a believer in that theory. So next week I will be purchasing new plugs and maybe wires too and will be changing out the fuel filter...Any other suggestions for good plugs would be greatly appreciated...I'll let you guys know how everything works out after I switch everything out and check the MPG'S again...

I would use AC delco plugs The truck was to design to run good with ac delco plugs

For plugs use the iridium plugs just like GM uses. And you might as well get plugs too, because when you go to take the plugs loose; they will come apart and don't buy the cheapest ones. They are crap in my opinion. Trust me on that I just went through it. What gears are in the rear end? Have you looked into a tune for your computer? I have read about numerous people getting tunes and their fuel economy goes up once they get through playing around and keeping their foot out of it. As far as the fuel filter... if you have changed it that often I do not see a reason to change it again. Have you tried running a different type of gasoline? Such as another brand? Just some ideas. And remember with the heat fuel economy does drop off too... atleast it does with my truck.

6.0s are notorious for terrible gas mileage, and yes your fuel economy will drop off in the summer, mostly due to a/c usage. and x2 for replacing the wires when/if you do plugs. worth the money and minimal effort.

Thanks for the tips...I'm gonna change plugs and wires(and I usually am one for not settling for the cheap stuff.. In response to Timber74wolf - I haven't thought of getting the computer tuned yet. The rear is 3:73. The fuell filter was only changed once since I purchased the trk and that was around 50,000 miles. Haven't tried running a different brand of fuel. I understand excessive heat and using AC will hamper the fuel mileage, but I still think my issues of lowsy mpg are more than that... Thanks again for all the suggestions....