I'm going back a few years here.. Mobil Avgas was always classed as 105-115 RON.. They couldn't be specific so it was about that level.. (marked as such on the 200L drums) BP 100 IS 100..
Methanol, (used to be Shell Racing A, and I had a couple of drums in my bedroom..mmmmmmm ) hmm don't be trying unless you're planning some serious tuning. Methanol is larger umm ' glob ' size and will not pass through the jets in carbed vehicles. The molocules will just block them, a tuning guide was jets needed to be about 3 times larger than for petrol. THEN... drain and flush the fuel each time you go to pack it away for the week or fortnight. Your oil needs to be either different or changed way more often.
That all said, as kids we'd run Methanol Injection on our cars for some fun. We'd build a water injection kit, drain the water and replace with Racing A which was vacuum injected STRAIGHT into the manifold.. we thought we were cool.. we used plastic fish tank line and fittings etc.. It was worth about 1.5 seconds at the Hill climbs. hahaha
insert witty comments here...