The use of Lead Tetraethyl will be prohibited, the anti detonation additive used in AVGAS, We already have grade 100 unleaded fuel for auto vehicles posessing the same anti knock properties.
However benzene chemical additive appears to be unsuited for aircraft application, prone to vapor lock and high altitude volatility due to its fast evaporation rate.
Benzene is also known to damage old rubber lines and carburettor floaters.
It's valve seat lubrication properties are disputed, considering the fact that lead content on 100LL gas is 0,5 grams per liter (!!) it must be quite a miracoulus agent to be able in such small quantities to perform such a task.
GAMI industries in the US has been a pioneer in the search for an alternative, they started creating multi cylinder monitoring instruments, and came up with a scientific approach to correctly leaning aircraft engines, which made both Lycoming and Continental techniques, dating back to the 30's of last century not only incorrect but obslolete.
Hope that a suitable alternative will be found, as these old lycoming and continental dynosaurs nearly 100 years old in design are definitely reliable, though AVGAS is insanely expensive nowadys and parts and engine replacements or overhauls costs more than a similar space age technology mercedes or ferrari engines...
https://gami.com/gamijectors/leantest.php
https://gami.com/paulferraris_leanofpeaksaga.pdf