With the exception of Sunoco the grades of gas sold in my area are 87 octane (regular), 89 octane (sometimes called plus), and 92 octane (premium). Sunoco has 93 octane also available called Ultra 93 (super).

Usually each octane grade is 10 cents more than the one below it. If 87 was $3.00, 89 would be $3.10, and 92 would be $3.20. Then they have their pricing wars where they will drop a couple of pennies off the lowest grade to bring people in only to find the better octane grades didn't change at all.

The cheapest gas close to me right now is 87 octane for $3.03 while the 89 octane is $3.13, and the 92 octane is $3.30. I talking self-serve stations with these prices. If they pump it for you, they may add as much as 10 cents a gallon.

Bob M