I always put Amoco Ultimate 93 octane in my '92 100S. When I first purchased it about 10 months ago, I experimented with sub-93 octane fuels. The car just did not run as smooth or seem to have as much power. Many say putting premium in the car is just a waste, but I stand by my decision. In my opinion, I'd stick with the 92-93 octane you had been using. Craig '92 100S (64k)