Just thought I'd share some info with everyone. Did my first upgrades to an '06 with the 3.5L, installed the Volant CAI and their cat back exhaust last week. Pre-upgrade I was getting 15 to 15.5 mpg city. Just filled up after draining the first full tank since the new hardware was done and came in at 17.5! I always burn Shell 89 octane. I was a little suprised it was that high, considering I'd been driving a little more lead footed than I usually do, loving the new growl, and the mpg increase is nice too! Haven't had a chance to do a highway comparison yet, but maxed at 20.1 once before the upgrades.

Dave

 

Bone stock 07 H3 3.7 , set the cruise at 60 mph and drove from PA to Florida via I-95. I got 20.6 and 20.9 respectively with 10% ethnaol gas. Was loaded with 4 passengers and the cago area was full lof luggage plus a hitch carrier rack with stuff on it.

 

Wow! You guys are doing well. I was excited when I just finally broke the 18 mpg mark. I am lead footed though. Rarely do under 70-75 on the interstate.

 

How many miles do you have to go at current gas prices before you break even on the parts and/or installation costs?

 

Here's a link to handy calculator: http://www.edmunds.com/calculators/gas-guzzler.html
For dgs101708's example I used $99 for the CAI and $250 for the cat back. I got these from Volant's web site and are damn good prices!!! Using 1000 miles a month, $3.00/gal and 2 mpg gain, payout is about 1.5 yrs (17,000 miles). Not bad.

 

The point of this reply is to let every one know that good mileage is achievable.
I have a stock 07 H3 with a K&N air filter, no other mods.
I just got back to Reno, NV from Burns OR (about 400 miles) and my average mileage was 20.95 MPG.
I'm not bragging, just letting people know that speed and fast starts are one reason I read about so many people getting low teens mileage.
I also like telling other people this information who are of the belief that all Hummers (H3's) are gas hogs.

 

Just got back last night , drove straight through from Lake Buena Vista to York, PA. 1,013 miles. Bone stock 07 H3. 5 adults , cargo area full of luggage and a hitch carrier with maybe 100 lbs on it.

At 70-72 mph I got 17.3 mpg AC on. Ethanol gas.

At 65 mph I got 19.8 AC on. Ethanol gas.

At 60-62 , no AC , no ethanol I got.....22.3 !!

 

One thing I've learned about the H3 is that the fuel economy is highly dependent on: 1) Rate of acceleration; 2) Anticipatory deceleration; 3) Highway speed. If you pay attention to the first two and keep highway speed to no more than 65 mph, you are more likely to break the 20 MPG (highway) barrier. MPG drops fast above that. Around 2,000-2,200 RPM seems to be the sweet spot for optimal MPG. I do most of my highway driving around 2,500 RPM. Headwinds and crosswinds will have a disproportionate impact on MPG, relative to a standard sedan, due to cd and total frontal/side profile area. Flat terrain and low MSL altitude will help on the plus side.

I have a 2007 3.7L with manual transmission. I run with regular fuel, Mobil 1 oil, nitrogen tire fill at 32 lbs, road force wheel balance (try it and you will never go back), and am just adding now a K&N drop in filter. I've been warned repeatedly by the dealer about the dangers of K&N with the mass airflow sensor, but after seeing the segment on the subject posted on their website, I thought I'd finally give it a try. Have thought about going further on performance intake and exhaust, but at only ~8,000 miles per year, it does not seem worth the money. No ethanol fuel will help performance as well--if you can find it.

Positives about my 2007 H3 (manual): 1) At 20 months and 16,000 miles, it has not had a single problem; 2) There are precious few vehicles that can do what an H3 can do--and live to tell about it. Its first test over Medano Pass in the Sangre de Cristo mountains and into the Great Sand Dunes told me a lot. Negatives: 1) I generally prefer manual transmissions, but this is a poor match--and I regret getting the manual. It is begging for a smoother shifting 6-speed, as compared with the clunky stock 5-speed; 2) The vehicle needs at least 260 foot pounds of torque and horsepower--particularly if you plan to use it at higher altitude and/or pull and trailer. With the additions notes above, including performance intake and exhaust, you can get close. BTW, if you plan to tow anything of significance, you definitely don't want the manual anyway. You will give up 1,500 pounds of towing capacity (3,000 lbs vs 4,500 lbs).

 

Great review Bullwinkle, thanks for sharing...and welcome to the group.

 

hehe not only u got an H3 but u got my next car the camaro, u trying to be me ?