Okay, so I got my 2001 Tahoe about a year ago. I didn't expect it would get great mileage, however, I am utterly surprised at how poor of mileage it does get.
When I was a kid my folks had a 1996 Chevy Suburban 4x4. We used it on long trips. It got 18 to 20 mpg NO JOKE on the highway. I was so surprised. Had a small block 350.
Now I have this smaller tahoe, it is the Z71 setup (not sure if that means different gearing too). Also has the 5.3 L. It gets MAYBE 14 MPG. Many times when I fill up is 11 or 12 MPG.
It does have BFG K02 tires on it. Although I'm assuming that's only partly why it's so poor mileage.
Curious, what kind of mileage are you guys getting with your Tahoe and suburbans?
Are you comparing apples to apples? I can believe (barely) that a 1996 Suburban would get 18-20 on the highway on a long, relatively flat road driven at moderate speeds (65 and under.)
I've gotten 18.5 and 19 mpg on my '04 Suburban on long highway trips.
It's stop-and-go that will kill your MPG. That Tahoe weighs more than 5,000lbs. That means every time you stop and start again you have to get 2 1/2 tons (or more) moving. In urban/suburban driving I rarely break 12mpg.
So are you getting 14mpg on the highway? And if so, what kind of highway driving are you doing? Is it a lot of stop and go? And what speed - consider that over 60mph MPG drops off sharply (most vehicles get their best mpg at 55mph.)
Next, how are you measuring your fuel consumption? Are you going by the gauge on the DIC? That may or may not be accurate but the only accurate way to measure is to calculate actual miles driven and divide by actual fuel consumed.
Finally, are you running stock tires? If your tires are oversize then your MPG is not as bad as you think it is - it's just that your oversize tires are 'under reporting' the miles driven. Measure distance with a GPS and compare it to what your odometer shows and then you will know what error to plug into your "miles driven" calculation.