I just happened to think that with these taller tires the milage that is shown on the trip meter is actually less than the milage driven be cause the meter is calibated for the stock tire size, right? If this is the case y gas milage should be slightly higher, or am I thinking backwards. Just for info I am getting right at 10 MPG around town. I am running 315/75/16 .Stock size is like 265/75/16Any thoughts??

 

your speedo is reading 9.3% too slow, speedo says 60 you are going 65.3 MPH

you are also traveling further than what the odometer is reading so in essence your mileage is shy and the MPG is also low.

 

Only way to know for sure is to get your speedo tested for accuracy.
My truck came with 265/75R16 stock and I put 305/70R16 on. Had the speedo tested and it was perfect. Within 0.5% I would have bet it was out 10%

 

At a rock steady 60 mph
10 miles of interstate highway mile posts
should go by in EXACTLY 10 minutes.

Each 10 seconds fast or slow means your speedo is off by 1 mph.

Don't try to measure just one milepost this way
because you can't time it right.

 

not having it corrected helps make the trips to the gas station feel more meaningful

 

I found out mine wasout by using my hand held gps. At 100 km/h I was actually doing 110 km/h.Stock is 235-75-16 and I brought the truck with 275-75-16. The stealership corrected it for $50.

 

This was my thought as well, I'm picking up my 98 Ram 1500 this Saturday, and I know the wheels/tires are different. Using my Garmin Legend is my only means of telling speed since all of the gauges (but not the dummy lights) aren't working. If cleaning the grounds and changing fuses doesn't fix it, all I'll have is my GPS.

There's always the option of getting on a four-lane road with a friend/family member, and having them match speeds with you, to see exactly how far off it is.

 

Over the last 10 years I have test driven more than 10 Dodge vehicles per year and the large majority of them had speedo/odo's that were reading about 4 to 6% fast.

Your factory warranty disappears 5% faster this way!

 

HankL Good to know, from pacing and talking on the CB with a buddy I was guessing I was5 mph fast, now running 6% taller tires I guess I will just call it even.Takes away my thoughts about an extra 6% of gas milage though, damn back to 11.2 mpg

 

Thanks for all the response, I would guess that yes I am getting slightly better milage. It just makes it seem better when you get 10% better milage i.e. 11 MPG instead of 10 MPG