I don’t know about in the Minneapolis area, but I have seen lube chain stores under the following oil brands: Valvoline, Pennzoil, and Quaker State. There may be others but these are some that I’ve seen and you don’t want to compete with their branding.
I think you should streamline this so that you’re not spending time trying to upsell customers from one synthetic to another. I would phase out the generic/no name synthetic and just carry ONE single brand of synthetic in multiple viscosities as needed. Mobil one is one of the more recognizable brands but then again, not everyone knows any kind of oil brand and many car owners have no knowledge of brands other than gasoline brands. If you just offer one brand of synthetic, you really streamline the process, no need for up selling, and your economy of scale for purchase discounts from just one distributor goes up so that even though you only have the one brand which is premium, you can either make more profit and or offer your customers better value. So, if you choose Mobil one for example, just offer Mobil one exclusively.