The other thing to consider, especially when storing fuel, is that the higher the octane the faster it loses the octane and goes off. I remember a few years ago at a stihl service school they had a letter from bp themselves stating that average 91 octane fuel begins to degrade substantially after about 10 days depending on conditions.
E10 is a whole other bag of worms, the ethanol is great, environmentally friendly etc, but it is plant based, and actually pulls water from the air. I don't know how many carburettors we used to clean that were full of water & had all the orings perish.
Fuel stabiliser is a fantastic product, never sold or promoted in a big way, but it definitely helps make fuel last longer
