I keep a spread sheet.... doesn't everyone?
So, the most I've done is 380.7 miles on 17.831 gallons
Date, Miles, Gal, Price, Time, MPG, MPH, Cost,Days,Cost/Day,Notes
05/28/2011, 71, , , , , , , , , New Car!
06/12/2011, 349.5, 15.841, $3.759, 7:30, 22.1, 46.60, $59.55, 15, $3.97, estimated time
06/30/2011, 360.1, 16.635, $3.629, 8:29, 21.6, 42.45, $60.37, 18, $3.35,
07/19/2011, 380.7, 17.831, $3.749, 8:58, 21.4, 42.46, $66.85, 19, $3.52,
08/04/2011, 380.2, 16.901, $3.829, 8:47, 22.5, 43.29, $64.71, 16, $4.04,
08/24/2011, 370.9, 16.664, $3.619, 8:25, 22.3, 44.07, $60.31, 20, $3.02,
10/02/2011, 377.9, 16.823, $3.459, 8:59, 22.5, 42.07, $58.19, 39, $1.49, retired on 31 Aug
11/17/2011, 352.2, 16.962, $3.429, 8:04, 20.8, 43.66, $58.16, 46, $1.26,
01/25/2012, 365.8, 17.331, $3.419, 8:27, 21.1, 43.29, $59.25, 69, $0.86,
03/15/2012, 364.5, 16.997, $3.869, 8:10, 21.4, 44.63, $65.76, 50, $1.32,
04/02/2012, 332.1, 15.467, $3.729, 7:37, 21.5, 43.60, $57.68, 18, $3.20,
06/08/2012, 316.3, 13.960, $3.519, 7:25, 22.7, 42.65, $49.13, 67, $0.73,
07/16/2012, 376.9, 16.701, $3.499, 8:05, 22.6, 46.63, $58.44, 38, $1.54, CEFCO