I've been wondering if there is a magic number for getting the most mileage out of your car? Out here the speed limit is 65 on the freeway, if I drive 65 and put the car on cruise control I get something like 46mpg, but if I slow to 63 I bump up my mpg, but piss off the people behind me, at 68 I get varying results, but mostly 50-60 miles per gallon. So, I've determined, very unscientifically mind you, that 68 is a good speed to drive. What I'm trying to figure out is what speeds help to maximize FE while maintaining freeway speed. Since in the city, between 30-40 you can get the electric motor to take over at any time given you have enough battery. The reason I ask is because I see many Priuses driving by at speeds I'd estimate at 70-80 miles per hour. I've driven 70-75 and seen various results, some including 73mpg, so I wonder if they know something I don't. Does this make sense? Here's what you should do if you want to help.

*Your make, model and year (I know it's probably in your profile, but humor me)
*The legal speed limit in your area
*Passenger's Yes/No. Any load whatsoever?
*Your "magic" number

In my case it's:
*2005 Toyota Prius
*65 miles per hour
*no passengers car is basically empty
*68 until I find another

In theory, I would guess that under ideal conditions this would give everyone the same ability to get the most FE out of their car, while maybe even learning something they didn't know about it.