Don't know why, but all of our cars are off. There was a big discusion about it back when the '05's were new. No one ever came up with a solution as far as I know.

 

Boeing 737

 

Awhile back Car and Driver had an article about speedo errors. I don't recall the specifics, but it confirms the errors and certain manufacturers were consistantly off.

 

Speedometers are almost always somewhat off and it has been this way forever on almost all cars. Remember also, as the tires wear (smaller diameter) this will also effect the speedometer reading. Even tire pressure changes will effect the reading.

So, not only are you registering more miles than you are driving on your odometer, you are not getting the gas mileage you think you are!

 

so this would change my mpg's by about 2 makes it even worse now

 

is your car an auto or a stick?? The waranty would be up sooner also. That right there could save ford tons of cash.
One other thought if I put 18 inch tires on my car would that make my speedo closer to being right ???? Right?? or do I have that backwards?

 

Another Mathemagician.

 

Once again, it's not the wheels that make the difference, it's the tires.