Sometimes I will commute to work on my bike and get lazy for whatever reason, then beg a ride home from my wife in the Prius. If a Prius has my bike in the back and it carries two people who ate a full lunch that day, has a full tank of gas at $4.19 per gallon and the bike is my 520 with 110psi in the tires and we travel 5 miles at 50 mph against a 12 mph headwind and I worked 1/2 hour of overtime that day, what is the savings, really, what is it?