How Does This Happen?

[daddy_dandy]

You should be getting better mileage, although not significantly higher. It's amazing what 2.5" dual exhaust and a tune can do for the Vortec engines. That's all I've done to mine and I pull 19-20 hwy, no problem and about 17-18 in the city. Running 3.73s and a 28" tire though.

 

[Fleeingpepper]

Yeah I always thought I should get better. 285s are like 33s so that can't help, coupled with the awful 3.42 gears. But my (future) brother in law has flowmasters on his truck, but he uses it for business now so he wants to trade me and get my quiet exhaust. Hopefully that'll help out. What kind of tune do you have?

 

[daddy_dandy]

3.42s are a great highway gear but terrible for running a tall tire. Concerning exhaust, I wasn't as concise as I should have been. 2.5" headers all the way back. I'm running a datalogged Wheatley tune right now. Will go 0411 when I get the cash for EFILive.

 

[Fleeingpepper]

As for being a great highway gear..the best I ever got was like 18 mpg with a 30-40 mph tailwind! So that's not too great. But maybe I'll get better mileage with these new tires. They're bigger, but they could roll better than the 265 el cheapo Chinese BFG knockoffs it had before.
I'm thinking towing is gonna be kind of annoying. Especially when I drove to Colorado.
It's kinda borderline but I am not gonna regear, I don't see it being worth the money since I gotta do the front and back.
Ahh..headers. Oh wellsies.

 

[97c1500]

i don't under stand how you all are getting such terrible gas mileage my 1997 C1500 5.7 Get an average of 18 or 19 always

 

[Butch]

My k1500 has always gotten 14 but lately it's been alittle worse as I haven't been doing a lot of highway travel. Change your front 02 sensors, they run about $90 but it'll be worth it as the computer will be giving a more accurate fuel/air mixture. Also try to change up your routine using roads with fewer red lights and using more right turns instead of left.

 

[Fleeingpepper]

I've always thought I've had emissions stuff going on. I've got p1351, p0103, p0138, p0420, and p0430.
Yeah blah blah the engine is being mean to the environment, I didn't think it would screw up the mileage too badly or anything.