[Arizona_928]

Good information here.

I’ve used isobutanol. Kinda pricy but it’s cheaper than the bottle stuff

Literature.

The “conventional” biofuel mandate was not specific to ethanol, and other biofuels could be used for compliance. One of the most promising nonethanol biofuels is isobutanol, or 2- methyl-1-propanol,6 which can be produced through fermen- tation routes similar to conventional ethanol. Like ethanol, isobutanol offers similar benefits: boosting the ON and with paraffins having a synergistic effect with isobutanol and olefins
lowering emissions when blended with gasoline. Compared to ethanol, isobutanol properties include higher energy density, lower moisture affinity (no phase separation), and lower vapor pressure.7 EPA approved isobutanol for blending into commercial gasoline up to 16 vol. % following a petition from Butamax Advanced Biofuels LLC.8 However, one of the primary barriers for the adoption of isobutanol, beside supply and availability of large volumes, has been the need to better understand the final octane properties after blending isobutanol with different gasoline blendstocks. ON must be measured prior to the sale of the fuel, and laboratory measurement of ON is costly and time-consuming.9 The ability to predict ON has been the subject of several studies in the literature.

https://www.osti.gov/servlets/purl/1660041