I use brand name gas, 91 (or higher) octane. These brand name fuels offer more clean engine additives (approved fuels for many high end autos) than billybobs econo stations. If your Audi Turbo's owner's manual lists BillyBob's - then it's OK for a scooter, if not - why chance it?
It is your scoot - but when I am riding regularly each week, I add nothing to the fuel tank or the oil. Just use good stuff (keep the valves adjusted, tires properly aired) and change that less-than-a-quart of oil very often (600 miles for me) It's only a Qt....cheap scooter insurance, don't cheap out - use good stuff. It will last a good long time with out additives (which may or may not do anything) In the winter follow the manual's instructions for sitting it idle. Me, I layer up and ride it.
Stig