Tires: tires and gas mileage, gas milage, gas mileage

Question
I drive a 2003 Ford Explorer, AWD with V8 engine and 57,000 miles. Up until recently I was getting approx. 12-14 in town mpg, now after the purchase of a new set of tires I am getting 10-12 in town mpg. The Dealer was out of stock on my tire size 245-65-R17 so I purchased the next size of 245-70-R17. Would this different tire size affect my gas mileage by the amount that it has fallen?

Answer
Hello, Earnest
Your gas milage is the same.  What has happened is the speedo is off by about 3.3%.  Its not reading correctly. When your going 60MPH you are really going about 62MPH.
On my Silverado they were able to adj it by changing the computer setup.