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Not to bust anybodies bubble but if you are running 245/75/R16 tires then your fuel economy is going to be skewed. Your spedo is off which in turn makes your odometer reading off which adds more miles than actually driven. I found this out when I got my GPS. I put 265/75/R16 tires on there and my spedo is right on now. So you might want to check that out. Tire weight is not the issue it the diameter of the tire. The larger the tire the slower the outer speed is going to be. That's where you lose most of your economy. Basically for every 3 to 4 miles subtract 1 to 1.5 miles from your total milage.

Lets say with 245/75R16 you can run 70mph at 2500rpm and get 22mpg

With 265/75/R16 you will get a lower speed @ the same rpm with reduced fuel economy because the odometer will read more correct.

on my old 245's I was getting 22 at 70mph but now with 265's I get that at about 65 according to my spedo.
 

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Both my all season 265/65 17's and winter 245/75 16's have the same diameter. I've tested both on a straightway with mile markers. Set the cruise exactly at 60 mph and took exactly 60 seconds. Not a GPS, but I'm satisfied my speedo is close.
 

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deamoncleaner...... according to the tire size caculator. your stock tire 265/65/17 has 29.6" diameter, and your 245/75/16's have a 30.5" diameter. speedometer reading with non stock tire is 3.1% too slow. when the speedo reads 60mph, you are actually traveling 61.8mph.

thats assuming the speedo was or is correct from the dealer. it's been discussed on other boards for a few years now, it seems a japaneese vehicles' speedo may say there going up to 3mph faster at 60mph..... a gps, on flat level ground is the only way to be sure....
 
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