We try to use "Premium" fuel of at least 91 octane (RON) in our 2018 RT Limited but have been told by the Service Department of a long-time Spyder dealer here in North Carolina that they have had no problems with owners running 89 octane.
I don't know where you live but if its available in your area, I would highly recommend you try and use ethanol-free gasoline. Even though your Spyder can tolerate up to 10% ethanol, we've been told by BMW automotive engineers in our area (there's a major BMW assembly plant in South Carolina) that ANY ethanol is bad over the long term.
There's an excellent website started by a motorcyclist in Wisconsin that attempts to list all the gas stations in the U.S. offering Ethanol-free gasoline. It is www.pure-gas.org. As you learn of new stations offering Ethanol-free gasoline you can add them. Similarly, if you find a station that no longer offers Ethanol-free gasoline you can remove it from the website. We've been using this website for years and find it extremely useful.