FWIW & IMHO:
There are several brands of octane restorer/gas restorer on the market. Even Wally World carries some. I would buy & put some in the tank rather than worry about it.
Best to pump out as much as you can and get rid of it, add AR LEAST a half tank of fresh to dilute the gallon of goo that will remain in the bottom of your tank...
If you need help pumping it out, let me know and I'll give you some instructions...