normal fuel was suppose to be 91-93 octane.. hioctane was suppose to be 97... however currently normal one when tested comes around 86-87.. while the best quality of hioctane comes close to 91... u can add fuel additives or octane boosters...
mixing fuel ain't a big deal.. u can do that,
internationally u can add upto 4% of water into fuel, while in pakistan its 8%, and at pump level it reaches upto 16%. u can consider hioctane as less adulterated fuel..
btw cng is 120 octane,