When you mix 10 percent 113 octane ethanol with 85 octane gasoline it increases the octane two points to the normal 87 octane most consumers use. So the higher the ethanol content, the higher the octane. The octane rating for E15 (15% ethanol) is 88 octane and E85 (85% ethanol) is 108 octane.
Subsequently, one may also ask, what gas has 10% ethanol?
E10 is gasoline with 10% ethanol content. E15 is gasoline with 15% ethanol content, and E85 is a fuel that may contain up to 85% fuel ethanol. The ethanol content of most of the motor gasoline sold in the United States does not exceed 10% by volume.
Is Shell gas ethanol free?
No. All gasoline brands have both pure and ethanol-containing gasoline under the same brand names. For example, Shell V-Power ranges from 91 to 93 octane both with and without added ethanol. It just varies from station to station, and it's up to the station owner whether or not to sell pure gas.