245 or 255/75/16

These Gas prices are killing me, currently running 265/75/16 and getting roughly 430kms a tank(light comes on) I know this has been asked a thousand times, but is it worth it to drop a couple sizes down.

 

It'll help, nothing drastic but you may pick up 1 mpg, maybe 2 if you're lucky. I about that going the other way, I went from 245/75R16 to 265/65R17 and lost about 1-2 MPG so it stands to reason that'd be what you would pick-up.

 

This Guy I talked to that has a set 255s for sale actually told me that going down too many sizes may actually be worse because now the wheels are spinning faster and will cause me to burn more fuel, It makes kinda makes sense

 

Are you running E-rated tires? Those 10 ply tires could be your weight issue.. drop down to a C or D rated tire and it might help some.

 

You sure you aren't just mis-calculating? Remember that your change in tire size is about 2.5mph different at 60, so over 300 miles, thats about 12 miles you've driven and not accounted for, which equals 1 mpg there, just from odometer error.

 

Dropping a few sizes like that really isn't going to gain you much. I didn't notice if you were running a 4cyl or 6cyl, but I would guess a 6 based on your mpg. It also depends a lot on the type of driving you do, as larger tires should help you on constant driving, but kills your mpg on stop and go.

Best thing you can really do is to go get yourself an ultra gauge/scan gauge and change your driving habits. For the cost to fill up one tank of gas, you can see real time how when you're punching the gas that you're now getting a whole 3 mpg. If your serious about saving gas, its going to end up being you that needs to change, or get a different vehicle.

 

I switched from the stock Dunlop Grandtreks P265/65/17 which were pretty much bald at 30000 miles, to a set of BFG All Terrain LT 245/70/17 and have noticed about a 2 mpg drop. I think it's from the new tires being heavier (E Rated), but it's a sacrifice Im willing to take to have better traction in the snow.

 

Hard to beleive that, what would it be like 20lbs extra(5 per tire) would make such a differance, that being said I am currently running 265/75/16 Toyo Open Country tires which are fairly aggresive and as an experiment put on a set of half baked 31/10.5/15 for a tank and I gained about 60 kms per tank. So basicaly I suppose if you work it out mathematicaly,tire and rim size and rotaion(all that stuff) it probably works out to the same.

 

So I looked at the sticker in the door jam and it list tires sizes, 255/75/16 in the first line and 265/75/16 2 other lines. What does this mean.

 

TRD vs. non TRD, mebbe they list both stock sizes on door. I know I've lost 2mpg going from 31x10.0x15 to 265/75/16 corrected by 2.2%. Strange thing is now my speedo/odo. is actually CORRECT going by GPS. I may need to drop that 2.2% which will put me back around 15.something mpg.

 

i'm getting 390ish with straigh city driving on 265/75/16 BFG AT KO's for the last tank....before that was MT's at 265/75/16's and about the same milage

my current tank will be alot more kms because it was mostly highway (albeit up and down hills going up to whistler)

 

There's no change in tire size for the example I gave, only a change in tire width. The difference between the 245/75R16 and the 265/65R17 is 0.09" so negligible in my book. Good points though with remembering to correct for your odo when calculating MPG's.

To the OP, if you went from a 265/75R16 to a 255/75R16 you'd be dropping 0.5" in overall diameter. That means when you're speedo is telling you 65, you're actually going 63.79 mph so it's not that far out. What the seller is telling you is partially correct and it depends on a lot of other factors like gearing, overall speed, etc.