[brucepick]

In the past I always used my car's odometer to measure mileage.

Early in 2011 I got an MPGuino, and in April competed in the 2011 Green Grand Prix (GGP). Planning for that event, I borrowed a GPS so I could calibrate the MPGuino as precisely as possible. I had about a 300 mile drive up to the GGP which gave me plenty mileage to compare the trip odometer with the GPS. I dialed in the MPGuino so it was now very closely matched to the GPS data, and subsequent driving with the GPS showed that calibration to be consistent.

Once I had the MPGuino calibrated from the GPS, I used the Guino distance for my fuel log. I think the carefully calibrated Guino data is more accurate than the car's odometer. Just my opinion.

From the point where I first calibrated the MPGuino based on the GPS, I used the Guino numbers in my gas log. When I later changed tires I tested it again and made an adjustment to the Guino setting to match the other tires.