Fuel for small engine (reciprocating engine) planes does indeed usually still contain lead.

> Unlike motor gasoline, which has been formulated since the 1970s to allow the use of platinum-content catalytic converters for pollution reduction, the most commonly used grades of avgas still contain tetraethyllead (TEL), a toxic substance used to prevent engine knocking (detonation). There are ongoing experiments aimed at eventually reducing or eliminating the use of TEL in aviation gasoline.

https://en.wikipedia.org/wiki/Avgas

Kind of interesting, but ethanol has SUPER high octane and could be used for avgas (although as we know with e85 cars, soft goods may need to be changed out). But using a mix of ethanol and gasoline can cause problems with water absorption and phase separation especially in cold conditions.

The water absorption and phase separation problems are particularly bad with airplanes because airplanes operate in very cold conditions when they go up to higher altitudes. I think that these problems also would apply to pure ethanol.

The other kicker with ethanol is that its energy density is significantly lower, so it would significantly negatively impact the range/payload of every small airplane.

The energy density issue is pretty small. You lose maybe 30%. This is tiny compared to the challenges of electric flight, for instance.

30% is huge for an aircraft. Not only do you need more fuel for each trip, you need extra fuel to handle carrying around the extra fuel. (not necessarily intuitive starting out but aircraft deal with amplification factors, energy added ounce of fuel will require a greater than unity number of additional ounces of fuel for equivalent performance)

Comparison to electric flight is a bad comparison as until very recently electric flight was basically considered to be impossible with present technology.

Electric flight in the history of flight has never been “impossible.” Anyone who told you it was impossible didn’t have the capacity/desire to think in terms of fundamentals beyond existing rules of thumb. (“Existing technology” is a nice weasel term, but we’ve had electric flight of various types demonstrated decades ago.)

30% is not high. It might convince you to do some drag reduction on your aircraft to compensate. Most small general aviation aircraft are terribly aerodynamically inefficient even compared to state of the art aircraft 50 years ago. 30% is barely relevant for the short intracity trips in this article.

I'm fairly certain these are leaded as well: https://www.seattleseaplanes.com/fleet-training.php