21 mpg this weekend on my nice long ride...
 

Very pleased with the mileage I got this weekend. '06 H-3 with just over
40k miles on it. Cruise set at 68mph and tires set to 36 lbs.

Just another reason why I love this truck so much.
My wife's Durango R/T with a 360 gets 12 mpg on it's best day !!!
The Hummer has now turned into our "gas-mileage" vehicle.

"Like Nothing Else"

I saw the same on a recent trip. It seems to me that it greatly depends on where I fill gas.

ah the memories... than I added a winch bumper, leveled the front end, added 315/75/16 tires, a cb antenna, hi lift jack, and hood handles... now Im getting close to your wife's durango ;)

[QUOTE=ZR-1 Mark;210599]Very pleased with the mileage I got this weekend. '06 H-3 with just over
40k miles on it. Cruise set at 68mph and tires set to 36 lbs.

ZR1- Mark,
I have a 07 (5 Speed) and I too have gotten 21+ MPG, but I drive about 62 MPH
with stock adventure package tires.
My only mod is DocOlds CAI
When I tell others of this mileage, they think I must be kidding.
I have some friends who don't know the difference between an H2 and an H3
Some friends !

That's great, guys! I need to drive a sensible speed some day and see what I can actually pull. Best I have got on an interstate run is about 18.5, but that's at 75-80.

Best I got on my 06 Lux was 20.5. Best so far on my 08 Lux is 18.8. No flatland trips yet and the 08 has roof rails which I think hurts the mpg. Also gasoline with 10% ethanol don't help matters either. I think if I removed the roof rails, did a flatland trip and used 100% gasoline I would get 20 on a trip. I think the 3.7 is a little thirstier than the 3.5. Didn't buy it for MPG's but it is comparable or better than most of it's counterparts....as if anything out there can actually compare to an H3.

I think I'm a sensible driver. Hummer always tends to stop rather than go due to box-like shape and weight. So nomally I just release the gas rather than push the brake to slow down. I have a 08 Alpha with 5.3L V8, which should be much thirstier than normal H3s. The best I got was 19.3 mpg during the summer. It was on I-70 in Colorado, which is kinda hilly and curvey. I'm using the #85 gas with 10% ethanol. My wife and I are short and thin (250 lbs in total?), not to much load. The average speed is between 65-70.

. I'm using the #85 gas with 10% ethanol. My wife and I are short and thin (250 lbs in total?), not to much load. The average speed is between 65-70.[/QUOTE]

Shale-
If you're referring to E85 (your #85) that gasoline it is 85 % ethanol not 10%
10% ethanol is what the rest of the country gets
You would definitely get better mileage with just 10% ethanol

I'm pretty sure he is referring to 85 octane. In missouri the lowest i see most places is 87, but 85 is pretty common in colorado for some reason.

Up here at the higher altitudes we have less oxygen in the air, therefore we require a lower octane fuel to get the same performance. 85, 87, 91 are the usual grades of gasoline in the "High Country".