Horrible gas mileage

[roundhouse]

If you use the ethanol free gas you will pick up 2 mpg

 

[LARGO9]

Bought a 2006 Tahoe about 9 month ago and the readout said I was getting 14mpg. 2 months ago told my buddy what I was getting and he show me how to reset the readout, now I'm getting 19 to 24 mpg. Try resetting your readout.

 

[MRM]

I had good luck with the BG 3 part fuel treatment. I had it done at an rv place. Really put the power back in it.
Firestone might have something similar.

 

[roundhouse]

Bought a 2006 Tahoe about 9 month ago and the readout said I was getting 14mpg. 2 months ago told my buddy what I was getting and he show me how to reset the readout, now I'm getting 19 to 24 mpg. Try resetting your readout.

You should also calculate it by hand
Dividing the fuel used by the miles driven

A lot of times the computer readout is intentionally optimistic

You may not even be gettin as good as you think

And if you installed taller tires the computer readout and the hand calculations will be lower than hey actually are

 

[rockyfatcat]

With that much oil consumption, you may have a broken/excessively worn ring/rings, possibly in only one or two cylinders. When changing spark plugs, check for heavy fouling/glazing. If only in 1 or 2 cyl., you could change only those plugs, maybe every other oil change. If it's not fouling plugs, could be valve guides.

The factory intake manifold had a bolt on belly. The original bolts installed at the factory were too long and shanked. When the seal leaks, it sucks crankcase oil into the intake. The fix is to remove, reseal, and replace the bolts, or replace the manifold with a Hughes/edelbrock