[bigredkitty1]

The higher the octane, the better the gas mileage. Just an FYI.

[Tupelo]

Wrong.
See post 20.
That is an old school from the days of the oil companies using tetraethyl lead to raise the octane rating.
Back in the early days most engines were very low compression. You would not believe how low. 4-5 to 1 or less. A high grade of kerosene would run most Model As. Read some of the horror stories about the “pool gas” from England after the war.

[jimmyray]

Quote: "The higher the octane, the better the gas mileage. Just an FYI."

Untrue. It depends on the octane requirements of the engine. Generally speaking, 91 octane in an engine designed for 87 will be less efficient, have lower power and will get worse gas mileage.

http://www.torquecars.com/articles/fuel-octane-ratings.php

[oscar_diggs]

The higher the octane, the better the gas mileage. Just an FYI.
*******
That is only true if your car requires premium.... putting regular in a car that needs premium forces the computer to retard timing to avoid knock which reduces mileage. Just put into it what the owners manual says...

[pelican001]

“The higher the octane, the better the gas mileage”

FALSE. The higher the octane rating, the greater the resistance to detonation (pinging).