I picked up a 2006 H3 Lux a few weeks ago and so far we love it...with the exception of the gas mileage. When doing research before buying the H3, everything that I found stated gas mileage of 16-20 mpg at least. I'm averaging more like 12 mpg, 50% highway and 50% city. I checked and changed the air filter and the psi is 45 all around and the mileage has not increased. The only reason why I bought this truck was the expected mpg of 16-20, not the 12 that I am currently getting and this is very disappointing. We drive the truck very conservatively and only drive 60-65 on the highway. Anyone else have this problem and if so is there a solution besides driving less or buying an H2?

 

How is buying an H2 a solution? Not sure were you are getting your 20MPG figure from (seeing EPA is 14 city and 18 highway) but 12MPG seems quite low if it is stock. I average 13.5MPG "city" (2 mile short drives to and from work kill my gas milage) but I get 17.5MPG on the highway. This is a 2008 with a 3.7L and 33x12.5 mud tires.

 

The 16-20 mpg was what I found by doing a Google search, but I checked out the epa estimate and you are right about the 14-18 mpg. I am thinking about checking the mass air flow sensor and if need be clean it. Other than that, I can't think of anything else other than putting in full synthetic oil and maybe an intake, but the difference has to be worth the cost.

 

i had a 07 lux,265 stock tires at apx 39 lb. i got a best of 20 on a trip,16-18 in town.
my 10 adv with 285 at 38,about 18 trip,15-17 mixed.
i think the 265 were the diff for me. if i wear out the 285, ill go back to 265.
u could need tune up stuff which you can find here.

 

My 06 h3 lux gets 14.9 mpg all stock factory size 265/75/16 tires.I live in the hills of ky no flat land here. 12 seems a little low o2 sensor?

 

What could need to be tuned that would affect mpg? I already replaced the air filter and from what I understand new plugs won't make a difference. How about the wires or the mass air flow sensor (cleaned not replaced)? I really do not want to dump tons of $$$$ for a slight mpg gain, the gains in mpg must be worth the cash!

 

The day we picked the H3 up from the dealer the check engine light came on, which was odd seeing as though we had the truck all weekend without incident. The dealer fixed it and said it was an O2 sensor. I personally think the young saleman was cruising around before we signed the papers as it took him over 30 minutes to put 5 gallons in and the gas station was accross the street from the dealer......and the 5 gallons he put in, yeah, we had the same amount driving out as we did driving in and the radio was turned to a rap station with the bass cranked. But anyway the O2 sensor has been replaced, any other thoughts or any way I can checked to ensure the sensor was actually replaced?

 

My H3 is a 2006 Adventure with 3.5 auto and the original 285/75R16 tires. vehicle is currently 100% stock although perhaps not for much longer

The best milage I ever had was just over 19 strictly interstate running 70-75. Maybe if I slowed down I could get 20 with a strong tailwind. The worst I ever did was 12. I am a photographer and in the summer we photograph high school seniors. So when we leave the studio we drive from one spot to the next and leave it idle for a few minutes in each spot with the AC on in hot weather. I have quit checking the milage on those tanks, that is when I get 12 MPG.

An average tank with a combination of city/hwy is usually about 16. I typically run 5-10 over the PSL on the hwy, sometimes a little more. But I like to think I am a smooth driver. I don't to jackrabbit starts and panic stops. I always try to anticipate what is happening ahead of me, sort of an H3 hypermiller

 

I agree with the others. Give it a tune up. New spark plugs can't hurt, just be sure and get OEM plugs... nothing performance. Synthetic oil is highly recommended. Clean the throttle body. Maybe get a bottle of RXP, and run it through a full gas tank to get all the crap out of the cylinders, and clean the injectors. Just my .02

 

Stock tire size?