My 74 Porsche 914 required 91 octane. I purchased it from a guy in Mira Mesa in 1987. By that time, the gas was tainted with MTBE. That stuff destroyed the rubber hoses in the fuel system. I've replaced the hoses completely on two occasions. A new fuel pump too. Annoying and expensive. The car has been parked in my garage in Idaho since 2001. No time, money or competent mechanics to keep the maintenance at the level required to keep it on the road.
My best ever premium leaded gas purchase in San Diego was 25.9 cents per gallon. It was a "gas war" in the Summer of 72. Too bad it was barely a one gallon purchase for my motorcycle.