At times the "lie-o-meter" and hand calculations are pretty close. If you've noticed when you start downhill and ease off the pedal, the mpg will really jump. When we had our 95 Crown Vic, we once actually got 32 mpg with it. We had gone to Austin and filled up (every drop of gas it would hold) before starting home. When we got home, we filled up again and we went 240 miles on 7.5 gallons.