I was discussing MPG of my Subaru with my father, a retired math professor, and he made a good point regarding MPG calculation. When fueling, especially when using the automatic shutoff feature on most pumps, the amount of fuel put in varies significantly. Therefore, if I just drove 250 miles and put in 10 gallons of gas, I might think my MPG was 25, not realizing this particular pump shutoff a half gallon sooner than the one from last fill up, causing an inflation of my actual MPG. If one is more interested in accurate Spot or Trip MPGs, one would have to put in a measured amount of fuel each time. Having a full tank is more important to me than this as the flucuations wash out for Lifetime MPG, of course.