ayuf sa analogy si yebo :hihihi

basta same octane rating

like what jtdc said, mixing a 50/50 octane will give you a mid octane rating of the two. Alam nyo ba na most gas stations offering three different types of octane rating usually has two tanks lang? i.e. 87 tank and 91 tank so may middle grade na sila na 89. (very true sa US)

based on my readings also, running higher octane by itself gave no benefit, except to make the fuel harder to auto-ignite, unless you retune your engine.

Check this out.
Mixing Octane Calculator

An info like this one is worth having it as a sticky **ahem** mods