Chevy Tahoe EPA MPG numbers optimistic?

I noted in a previous post that although the 2007 Tahoe's EPA mileage numbers aren't exactly stellar, they're far better than they were only a few years ago. The 2007 Tahoe 2wd 5.3 is EPA rated at 16 MPG city / 22 MPG highway.

But I may have spoken too soon about the apparent frugality of the new 'Hoe. Reports on the Web are reflecting real-world mileage figures that are significantly poorer than the advertised 16/22.

MPH Online's Blog notes

I just managed a paltry 16.3 mpg in a 2007 Tahoe on my 50-mile (each way) daily commute, 90 percent of which is highway driving. The problem? The 4-wheel drive Tahoe claims a fuel economy of 15 city, 22 highway. The last Tahoe I drove, which I took to Chicago, only gave back 14 miles per gallon. That truck had barely any miles on it and was a preproduction unit, so I was willing to give it the benefit of the doubt. But that's not the case here since the more recent 'Hoe was well above its break-in miles

A thread on Chevrolet Forum asks users of their MPG, assuming 50-75% highway driving:

Viperjuice posts: well i've been driving back and forth to work some city some highway and i average about 15.. i had it on the Masspike, which is alot of up and down highway and i reset it and was getting only 16.8.. honestly i'd go with the trailerblazer with the dod v8.. lighter truck, therefore better mileage.. and they defenitly are much better than those l6 engines.

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Swatson1 posts: I'm getting 13.7 mpg overall average in my LTZ. I drive about the same percentage of hwy and city miles. I'm severely dissapointed in the gas mileage. It seems to make a difference whether you run the a/c or not. I'm in texas where it is hot, so I run it a lot.

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ZX1100F1 posts: I have a 4X4 model with 4.10 gears, I get about 16.5 MPG avg with about 50/50 Hwy/City driving, I just turned 3K miles last week.
I took a trip the first week I owned it and avg'd a little over 18 Hwy, got 455 miles one tank before the light came on and I filled it up

You get the picture. So what's the problem? Active Fuel Management. My own theory is that the software algorithm behind this feature on the 5.3 Tahoe is optimized for the EPA test cycle but not necessarily for real-world driving conditions. Or perhaps the software has been revised between the test and the release of the vehicle. Or heck, maybe GM slipped the EPA a ringer.

In any case, I had considered the Tahoe despite its borderline-lousy MPG, for its utility and comfort. A herniated disc requires me to drive a vehicle with big seats, a high seating position, and plenty of legroom. But if the mileage is as bad as user reviews have indicated, the deal is off.