Anyone else use GPS to see if the odometer is off? Not sure how accurate my GPS app is on my phone but it's showing .15 mi more that what my odometer shows (although the odometer doesn't go to the hundredth so it might be less difference). I guess if it's accurate that's a good thing because it's putting about 2% less miles on the truck than it's actually traveling. 100k miles would only show as 98k on the odometer.

 

my previous car was like that, my truck seems accurate.
but like you say, it's 2%... at 100,000 miles, that's 2,000 miles. seems like a big number, but that wont really affect your resale value or anything else... unless you have a warranty claim at 1.5% over the mileage limit?

 

After switching to 285/65/18 tires I thought the speedometer would be off by at least 2-3mph at 60 or 70mph but it's spot on.

This leads me to assume Ford is cheating in their EPA rating for MPG. When I swapped to shorter 3.73 gear on my mustang while running a tune still for 3.31 gears the computer was registering 24.8mpg around town which was nearly 5-6mpg more than before. After retuning it's now back to the usual 18-19mpg.

At about 3-4mph off that's like 5-7% difference which would effectively boost the computers calculation of mpg by 1-2mpg.

The stock tire size was 31.9" and the new tires are like 32.7" so there should be a slightly noticeable difference.

 

GPS is only accurate within 7.8 Meters. I'd rather the truck be the lower of the two anyways. lol. Only way to know for sure is to clock it with the mile markers on the road.

 

Mile markers aren't always accurate either. I do agree I'd rather have the truck having the lower amount.