Today, octane is raised primarily by adding ethanol. Most gasoline sold in the United States today is e10, which is a blend of 10 percent ethanol and 90 percent gasoline. Fuel ethanol has an average octane rating of 115.
Refiners typically produce 84-octane gasoline that is blended with ethanol to make regular, 87-octane e10, and 88-octane gas that mixes to create 91-octane e10.
There are other octane boosters, but they are more expensive. More of those costly additives are needed to boost the pre-blended fuel four more points to 88.
These expensive octane additives also are much of the reason why 100 percent gasoline without an ethanol blend tends to cost more than e10.
I am looking to replace my 15-year-old Chevy Lumina. One requirement I have in a new vehicle is that it does not have a fancy engine designed for high-octane fuel.