Thanks for the reply. Car originally had 17" wheels and was damaged dodging a deer and hitting a culvert. Broke the right front lower support and the wheel. Original tires were 235/45/17 and matched the door sticker. When I repaired the damage I switched to 16" wheels and have 215/60/16 tires installed, which are the same revolutions/mile as the 17" tires. The speedometer was off by the same amount before tires were changed. Changing to 215/55/16 tires would bring the speedometer in line at 800 revolutions/mile instead of 717 r/m with the present tires. New tires are Michelin MVX4 energy and have about 12,000 miles on them now. Guess I'll have to wait untill these tires need to be replaced. It seems odd to me that there is not some way to download a new factor into the computer to correct this. Even my '93 Ford 250 has this feature. Corrected for error, the car is getting 31.2 mpg on the road at 70mph carrying me (175#) and 200# of tools and equipment. Not bad!!!