If you’ve been around the aviation industry long at all, you probably remember when, a few years ago, there was a highly visible push to eliminate the lead component of aviation gasoline, even if the amount of the toxic substance in 100LL aviation gasoline is reduced from its predecessor fuels. In 2014, the FAA and industry got together and formed the Piston Aviation Fuels Initiative (PAFI), which was established to identify, evaluate and deploy some kind of replacement for 100LL. According to the FAA, “Avgas emissions have become the largest contributor to the relatively low levels of lead emissions produced in this country.” Unfortunately, replacing 100LL is a lot harder to do than it is to say.
One of the biggest obstacles to an unleaded avgas is compatibility, both with 100LL when mixed in the same tank and with the various engines it will fuel. Keep in mind your engine and airplane likely were certified for 100LL. What happens when you put something else in? (Yes, we know about mogas options, but they only exist for relatively low-powered engines.)
