It's not actually a secret. The abundant, affordable low-octane base fuel stocks that refiners and blenders work to bring up to specs have always been a no-bra

It's not actually a secret. The abundant, affordable low-octane base fuel stocks that refiners and blenders work to bring up to specs have always been a no-brainer - just add a few grams of lead to your tank, and wow you've got high-octane rated fuel. And lead is heavy so that's only like a small number of mL. Very few oil wells naturally yield a very high octane gasoline fraction, so for adequate engine performance, some enhancement has always been necessary. The "pipeline" ended up being built basically around gasoline and additive, where the additive amount directly and straightforwardly controls the octane. Alcohols were always known to bring up the octane rating too but you need to add gallons of alcohols to your tank not just grams. However the energy density is lower with alcohol so you get fewer miles per gallon, not what you want in an aircraft. Well this is more like blending two bulk fuels so that was one of the infrastructure adjustments that needed to be made as the lead additive approach was phased out. Now major percentages of alcohol are blended with base stocks to achieve the target "clean-air" and octane-rating requirements, so this has been well in place for decades. For the G100UL they do not use alcohol, instead they blend in many gallons of other flammable liquids like xylene, which is a hydrocarbon itself, just happens to increase the octane, and increases the energy density as well. Xylene is traditionally handled as a solvent and paint thinner, so they can get trailerloads (but not nearly as cheaply as alcohol is in automotive gasoline). Xylene has always been one of those dangerous flammable hydrocarbon cargoes, supplied as a petro-chemical by a lot of refineries, it's just one of the chemicals that is normally considered too expensive to burn. So they're not replacing a few grams of lead with a few grams of something else, GAMI has replaced a few grams of lead with a few gallons of something else completely different from lead. And that "something else" are actually hydrocarbons that have always existed naturally in all kinds of gasoline (only in far less significant percentage). GAMI is scientifically bringing up the percentage of this type of component while maintaining the drop-in characteristic.