A 10-mile run will tell you nothing...that is still within the margin of error. The only way you will validate the odometer is by taking a 100-mile trip. At the start, set your trip meter to 0 and set the GPS trip to 0...any bride you go under or any tunnel you go through will throw the results off. The straiter the road, the more acurate...mountain roads are out. If it is done this way and I'm wrong, I'll pay up. I'll also be very surprized if your GPS reads 100.0-miles and your odometer doesn't read something like 105.