H3 MPG < H2 MPG
 

WHy is my H3 with 35" tires getting 3-4 mpg worse than my H2 with 37" tires? I'm only geting around 9mpg in the H3 and am getting 12-13mpg in the H2. They both have the same tire tread, both have stealth GOBI racks, both get gas from the same station, and I drive both the same.

:confused:

Re: H3 MPG < H2 MPG
 

Could it be that with the H3 only having a 3.5L engine and trying to move 4700 lbs of vehicle with taller tires is more taxing on the engine than a 6.0L (or whatever is in the H2) trying to move around a slightly heavier vehicle with taller tires, but not as taxing to the engine?

Seriously though, the little H3 is overworked to begin with, and the addition of taller tires makes it have to work just that much harder. That extra work comes at the cost of the fuel economy, whereas the H2 has power to spare and can handle the taller tires easier.

Re: H3 MPG < H2 MPG
 

In case you didn't know, Hummers are not about saving Gas. Maybe you have this site confused with the jeep or VW site. Rebel

Re: H3 MPG < H2 MPG
 

Have you had your H3 odo recalibrated? If you're running 35" with factory calibration on odo, then you are getting more miles than you think.

Re: H3 MPG < H2 MPG
 

9 mpg sounds REALLY low! I'm still averaging 14-15mpg with my 35's. Granted I don't have a roof rack, but I doubt the Gobi will account for 5-6mpg.

Re: H3 MPG < H2 MPG
 

The 35" tires are severely over-working the hamsters.:jump:

Re: H3 MPG < H2 MPG
 

Something's wrong with your H3 maybe. I'm running stock 32's on my H3 and averaging 14-16mpg over last 16 months.

Don't think the 35's should hurt the mileage that much, just make it more gutless from a street acceleration standpoint.

S.

Re: H3 MPG < H2 MPG
 

IMO two things may be at play here, first is the diameter difference in tires, since w/315/75/16 you are going 3.5 mph faster than w/285/75/16 therefore farther distance traveled with each revolution your odo is not showing true distance making your mpg caculations off (to my knowledge no one recalibrates speedo for h3 as of this time) second when you went to 35's did you also go M/T I was getting about 17.5mpg on highway w/stock 33's, changed to 33 in bfg mt and dropped to 14.85 mpg on highway(higher resistance tire = worse mpg)

Re: H3 MPG < H2 MPG
 

wondering if I should but fat tires on the beatch

Re: H3 MPG < H2 MPG
 

:iagree:

Just guessing, but another problem could be the torsion lift changing the aerodynamics of the front end and underbody.

Re: H3 MPG < H2 MPG
 

It's pretty obvious. The less MPG your vehicle gets, the cooler it is. The cooler your vehicle is, the less MPG it gets.

Re: H3 MPG < H2 MPG
 

Just did some calculations on your estimated tire diameter (C = pi * d). Assuming an actual diameter of 33 and 35 inches, your tire circumference changed from 103.62 to 109.9 inches, so you're now travelling 6.28 inches further with each tire revolution than your odometer reads.

To convert your mpg, find the ratio of one circumference to the other and multiply by your odometer's mileage.

109.9/103.62 = 1.06%

9 mpg * 1.06 = 9.5 mpg (corrected)

That's not very much. Maybe aerodynamics from the t-bar lift makes a bigger difference. Other factors could be tire pressure, cargo load and driving patterns.

Somebody please check my math. My algegra's a little rusty.

Re: H3 MPG < H2 MPG
 

the engine has nothing to do with how much its going to burn relatively. Its called the conservation of energy. If you have the same mass, and try to move it with a smaller engine, it will be at higher rpm, but use less fuel per revolution because of the smaller size. A larger engine would do it at less rpm (thus seems easier) however because of its larger size uses more fuel per revolution. 3.5L to 6L almost double per revolution. Although its more complicated than that, i just wanted to make the point.

Tires however could be an issue.

Re: H3 MPG < H2 MPG
 

I have a 5 turns on t-bar as well as roof rack w/pull pall and highlift jack I noticed a slight drop after t-bar crank (1/4 mpg) but never put crank/aerodynamics together. figured I was just getting a little more into the skinny pedal than before. major drop after I added M/T's

Re: H3 MPG < H2 MPG
 

Well, we found the issue. One of the mahsters under the hood was tired so we added another.

http://www.transoniq.com/images/ham40.jpg

I hope this solves the problem.

Re: H3 MPG < H2 MPG
 

I still think it's the Gobi. I don't know about everyone else, but I'm going to spread the word that it will cut your MPG in half, that's ridiculous.

Re: H3 MPG < H2 MPG
 

Timgo,
Check and see if one of the Hamsters is lodged in your intake manifold:beerchug:

Re: H3 MPG < H2 MPG
 

:jump:

Re: H3 MPG < H2 MPG
 

i have the rancho lift with 35 inch superswampers and i get an indicated 10-11 mpg.
cant see hpw ur getting an indicated 9mpg.
i realize the odo is off, but guys like us are hurting.
if i knew the gas mileage would be this bad, i would have gotten an h2 and lifted that..:)
probably my next vehicle, but i really like how the lifted h3 offroads.