"So, my engine... Certified to run on 73 octane ran on 80/87 with 0.14 g/l of TEL until it became "environmental" and went to 100LL...
The LL standing for Low Lead because it "ONLY" has a fraction* of 80/87's (0.14) TEL. It has 0.56...
That fraction is... lets see 0.56 / 0.14... That would be 4/1... Uh... That's 4/1... Not 1/4...
"Modern Truth" like "New Math.""
100 LL is not intended to be lower lead than 80/87, but rather the 100 octane that it replaced, which had much more TEL in it.
The 100 LL is not intended to replace the lower octane product, but as the use of 80/87 decreases, fewer airports sell it, and the low octane engines, by default, burn 100 LL.
For those with homebuilt, or engines approved for MO gas, there is a no lead alternative, but with a possible downside. MO gas has dissolved volatile hydrocarbons to increase its evaporation in a cold engine, producing an elevated possibility of vapor lock. High wing planes are generally not subject to this problem, Cessna 177 Cardinal is an example of an exception, part of the reason they have an electric boost pump. The presence of ethanol and other ingredients results in relatively rapid deterioration of MO gas, which becomes a safety factor if the plane is parked too long.
MO gas went bad in my lawn mower over the winter, so I drain it in the fall, rather than deal with cleaning the carburetor in the spring. My emergency generator has only had AV gas since I bought it, and this year, I have been depleting it by using it in the lawn mower. The 4 year old gas in the generator is still just fine, but when it is empty, I will refill with fresh, stable AV gas again.
Aviation gas is a superior fuel in many respects, and to me, well worth the additional cost in flying, and uses where long term storage is a normal condition.