I've noticed that there's a maximum gas mileage in both automatics that I drive that around 42mph I can get 44 and 42 miles per gallon. This seems to be the lowest RPMs needed to not lose speed on flat ground at that speed, in the highest gear (4th).
What do you cars get?
Subary Legacy wagon - 44mpg
Chevy Venture van - 42mpg
EDIT: Just as clarification, I meant the highest for flat ground while on the accelerator, not the highest gas mileage using technique.
There is no flat ground nearby so I coast out of habit. But the best I've gotten keeping the car above 40 is about 38mpg, using 40mpg as top speed and gliding down to 20mph I was able to get it up to 47.55.
Maybe there is something wrong with my Subaru???
"If you want to save gas I suggest you permanently remove the drivers seat and steering wheel. That seems to help." -Oscar Halverson
2.7L/100km over a 249.2 mile course, mostly repeated out and back loops on interstate with a semi-urban access drive to and from the start-finish and the highway. The 87.1 mpg on B100 biodiesel was converted to a BTU equivalent and then to a gasoline mpg equivalent to allow comparison of different fuels in the competitor's vehicles. The 2003 Tour de Sol official 83MPG(e) reflects this gasoline equivalent fuel efficiency.
Next best was 77+ mpg, again on B100, over a 500+ mile course in 2005.