Gasolines have its ratings depending on its autoignition resistance when ignited by spark. The higher the rating, the better on fuel burning and easy starting. I don't know how they have utilized this on hybrids.
Octane boosters claim to significantly raise fuel octane. A typical 92 or 93 octane pump gas contains hydrocarbons that evaporate in a range from about 80 degrees F to over 400 degrees.