Hey guys,

Sorry for the inconvienience but I have been averring about 12MPG with my 2006 Hummer H3. I have 325/70/R20 i know those are really bad for the MPG but I wonder, What is the average MPG you guys get? Please list the type of tire and tim you guys are using because I want to change my Tire and Rim size to the best MPG without the Hummer looking weak!

Thank you,

BumChuck

 

With that size tire, your mpg's sound about right and are obviously going to be worse than the advertised 14/18mpg's that the H3 would get with stock tires.

A couple things that may help mpg's a bit.
1) Make sure you are running enough psi's in the tires. I'd run as much as possible without having the ride suffer or losing full contact patch. (A chalk test on the tread will tell you if you have good contact to ensure even treadwear.)

2) Depending on how many miles you have on your rig, a TB cleaning may be in order and perhaps running a fuel system cleaner to ensure the injectors are clean.

Other than those items, not much you can do to help the mpg's you are getting other than replacing the tires back to a smaller diameter as you are contemplating, or re-gearing the diffs to suit the tires you currently have.

 

I've got an 06 H3, and we run stock tires that came on the rig 285/75/16 on stock rims, aggressive for us, I traveled recently 1800 miles and got 20 to 24 mpg. Average speed was 60 mph.
I am now running cleaner every 3 tanks of fuel, we only have 33k on the rig so its just broken in.

Good luck with the tire issue!!!

 

I get 12 to 14 range with 295/70/18. Are you sure that size is correct because I am showing that as a 38" tall tire and I have never seen an H3 that can pull that big of a tire with the I-5

 

How are you pulling off 20 to 24 mpgs???? i think we all need a better explanation!

 

I think he gave the explanation, 60 mph. All the mods we do to improve mileage will never be as effective as simply slowing down. The first summer I had my 3 there was construction the majority of my 100 mile daily round-trip which limited my speed to 60(flow of traffic, i don't speed through those zones by myself) and was regularly getting 19-20 mpg's.

For the OP, both 265's and 285's came from the factory on these trucks and, from many reports from many drivers, achieve the same mileage. IMO, 285's give a good balance of looking good and keeping good mileage. 265's are fine but leaves a lot of wheel well visible.

Edit: Due to your location it may be a little more difficult to find used stock 16" rims but they come up on craigslist/ebay all the time for $25-50/rim

 

Are you taking into account the non-factory size tires making your speedometer/odometer not being correct unless you have had it calibrated? You may be getting less than you think.

 

On a trip,to AVERAGE 60 you are flying. to get good mileage you might need a max speed of 60.
I usually end up hitting 70-85 on top. Averaging 60 is not easy,within the law.

If I did a max of 60 I think i could get into the 20's,might just try it on my next long run.

 

Happy3> I think when most people say they average "XX" mph on a trip they are refering to the highway portion of the trip.

 

My H3 has just over 26k miles on it! It was parked for almost 3 years! The PSI on my tires are just about 38PSI. The tires Are HUGE as you can see! But Thank you for the advice. I'm going to try the Cleaner.

Yeah, Thats the right size! 325/75/R20 Pirelli Scorpions! I asuming thats the reason why my MPG's are so LOW! Trying to get up to 15-18 because gas here is over $5 a gallon.

Yeah, I am sure that it has been calibrated because I also run the calculations that i travel by had! it you go to fully.com and search for BIG RED you'll see my comments on the travels I do. But thank you for the comment!

All I need now is to find like Widespread Hummer said look for the Rims for the H3 Chrome on Craigslist/eBay which I hope I can as soon as possible!

Thank you guys for the comments!