Thomas,
TEL doesn’t really lubricate guides or valve seats. It is thought to provide some “cushioning” effects but hardened seats provide the same protection. And all aircraft engines have hardened seats. The lead in 100LL is four times the lead that was present in leaded 80-87 octane aviation gas that many engines were designed to run on, hence, lead fouling is a real problem on engines which do not require 100LL. The lead also makes the oil dirtier, and as it reacts to the combustion process can leave deposits of lead salts on the valve guides, which is the major cause of stuck valves in GA airplanes.
The octane ratings of Mogas are expressed as (RON+MON)/2=AKI; or the average of Research Octane Number (RON is determined by running the fuel in a test engine with a variable compression ratio under controlled conditions) and Motor Octane Number (MON is determined at 900 rpm engine speed instead of the 600 rpm for RON and is lower than RON)
and AKI is the Anti Knock Index. So 91 RON in Germany is equal to 87 AKI in the USA. With an 8 - 12 Octane Number difference between RON and MON.
Hope this helps,
Dave