So according to the Turner,s" Handbook Tuning Manual" the general guidelines for octane usage for Compression Ratios are..
8.0-8.5 ..87-89 octane
9.0-9.5...90-91 octane
10.0-10.5...91-93 octane
Dazon lists the GY6 compression ratio for their motors at 9.5:1. So it is at the 90-91 octane rating scale for this stock motor. However some GY6s have more and some have less . If the motor is modified or has a little carbon on the piston that can change it too. I have been using 87 for a while because the motor was stock and it is cheap. Now modified... i am going from the bottom to the top levels to find the best one to use. Sometimes you need something in the middle so you blend it by mixing 1/2 gal to 1/2 gal. Lets say you want a 92 octane gas just mix 91 and 93 together. With grades from 87 to 114 this may take a while.
