MPG's are really begining to suck

[fyremanpat]

Recently Ive began to notice my mileage really beginning to suck. Im running 305/75/16's with 3.42 gears and use to get close to or around 300 miles to the tank, now it's just over 200 miles. Granted I let the truck warm up in the mornings a little but not enough to lose almost 100 miles per tank. Would running a hypertech programmer not cause a CEL due to the engine parameters being different? Im not losing coolant or oil and I just put new plugs, cap and rotor in it.

 

[bowtiefreak]

One thing to keep in mind is that in the winter the fuel companies change the gas a little causing worse milage. The 3.42 gears are not ideal for a 33, but that would not cause a drop like that. I have seen my milage fall off as well. My stock suburban is getting 11-12 right now.

 

[BigDaddy13440]

Recently Ive began to notice my mileage really beginning to suck. Im running 305/75/16's with 3.42 gears and use to get close to or around 300 miles to the tank, now it's just over 200 miles. Granted I let the truck warm up in the mornings a little but not enough to lose almost 100 miles per tank. Would running a hypertech programmer not cause a CEL due to the engine parameters being different? Im not losing coolant or oil and I just put new plugs, cap and rotor in it.

305/70's or 315/75's?

305's are the same diameter as my 285/75's, but I've got 3.73's in mine. I'm averaging about 12 mpg (by the odometer), if figuring in the conversion from the stock 245's it's actually close to 13.5 mpg (32.8"/30.4" x 12= 13.5).

I'm sure I'd get a bit better mileage if I had 4:11's, but I don't think it'd be enough to pay for the cost of regearing. One mile a gallon would save me about 7 cents per mile driven, I'd have to drive 10,000 miles to save $700, not even enough to cover the gears alone.

 

[fyremanpat]

305/70's or 315/75's?

Oops...305/70/16

---------- Post added at 10:57 AM ---------- Previous post was at 10:55 AM ----------

She still runs great and idles smooth. I wonder if maybe my brakes are dragging since all the salt and sand on the roads..i dunno...at 60-70 bucks a tank, an extra 100 miles gos a long way.

 

[brooks93]

my 96 5.7 with 3.73 and 285/70/17 tires (156k miles) is getting just over 17 mpg or 400 to 450 a tank. Granted I have changed plugs, wires, cap, rotor, air cleaner, new mpfi injectors, fuel filter, and fuel pump. When I first got it I was getting 12 to 13 (144k miles)

I have also done a 0411 pcm swap and have a black bear tune

 

[fyremanpat]

Ive done all but new injectors, 0411, and black bear tune

 

[longstand]

Ive done all but new injectors, 0411, and black bear tune

What is "I have also done a 0411 pcm swap and have a black bear tune"

My Denali is getting a very bad MPG

what can i do or mod to get more MPG

i Sea-Foam the whole Engine.
K/N Filter

New Fuel Fiter, Fuel Pump. New Oil Change,

 

[BigDaddy13440]

Ive done all but new injectors, 0411, and black bear tune

ditto.


I've got a '96 Vortec, how difficult/expensive is it to do the injectors and the 0411 PCM? Any info would be appreciated.

 

[96ProCompTahoe]

heres the 0411 thread from a little while back:

http://www.tahoeyukonforum.com/forum/showthread.php?t=20310&highlight=0411

 

[fyremanpat]

hmmmm....Just three hours or so huh? Might have to look into this. I always thought it was a lot more