I use Arco here as normally 40 cents less per gallon than Shell, used it many years here and in UT in many different tuned vehicles, never had an issue.
I have not verified if they are keeping the winter blend full time, just saw Goldengate is closer to Shell prices, not blended. They sell the regular grades, E85, unleaded 100 octane race gas at $6.95, etc so their 91 might be pretty good gas.
I use 91 in our V8 4runner, will run OK on 87 but they recommend 91 or higher for better performance and it does run significantly better so the mileage might be a bit higher on it, never checked it out but I should do so. The Goldengate straight 91 might work out well so will check into it as well.
I ran Chevron for many many years before switching to Arco, usually no Shell stations around.