I have a question for those with an h3 that have 285 75 16 tires! Did you notice a significant decrease in your gas mileage after switching? I know we don't get very good gas mileage to begin with but I don't want it to be terribly worse!

Thanks in advance!

 

not a significant drop, maybe a 1/4 mpg

 

my 07,265 stock got just barely 20 on a turnpike trip.

got a 10,same 3.7 with 285, best is 18,maybe!

 

I assume since I have him blocked that tom said something about his 07 getting this and his 10 getting lower. Two different vehicles will get 2 different fuel milage readings. We have had 3 08 Alphas an they ALL got different mileage readings. If he would have said he changed tires size on the same vehicle and documented the difference in mileage then his input would have "value"!

As far as 285s from 265s. We have never owned an I5 with 265s so I can't really help you there. Plenty of others here have done the swap to 285s (even to 295s, 305s and 315s). Hope they will chime in and give you some decent info that has "real value".

 

Pretty much the same for me.....1 year on 285's with '09 Lux I5.

Avg about 14 - 14.5 overall when warm out...now in winter down to 12.5-13.0.

 

yeah,best i could offer,not gonna buy a new set just to find out!!

ill trade ya guys for 265s. i got abt 17000


thinking about it, what other major diff btwn the 2 h3 that would/could cause 2 mpg.
its prob the tyres. youd think the newer would beat the 57000 miler even up
so it must be the tires.
now if we had 2 exactly same with same mileage,like 57000 then that would be an accurate comp.
so none of the comparisons are accurate,except most guys report a drop in mpg when goin up to 285+

 

We all know when we bought our Hummers, it was not for good gas mileage. If that's a concern, you need to look at trading in on something else.

 

Probably due more to pre-set shift points on the automatic not being optimized than anything else. A PCM tune will correct that and your speedo for you.

Keep in mind the actual weight of the tire will come into play as well, unsprung weight can be a real bitch. If you are going to a heavier duty tire of the same size as your current one it will more negitively affect your gas mileage than if you went to a larger dia. light duty tire.

I noticed a reduction in my gas mileage when I went from 285 (which were the OEM size on mine) to a 315... it is important to note my tires went from being 80lbs each to 115lbs each. Recently I changed out my stock rims to something lighter and dropped that back to about 100lbs... same tires, but gas mileage is much better now.

I also have a manual, so I determine my own ideal shift points... which takes the edge of the gas mileage when going to a larger size.

 

From 265's to 305's, I saw at most a 1/2MPG change in both city and highway.

 

I have the stock 265's on mine now. My mileage sucks! Now is it better than my '02 F150 4X4? YES! I beat my F-150 by about 2 MPG. My '07 H3 runs around 14 around town and about 16 on the highway. I'm gonna need tires soon so my big decision is 285's or 305's or 315's. Not alot of wheeling, but do enjoy checking traps or hunting deer in the H3.

It's nice to hear that going with the 265's won't help me much