Here in Canada we can get a 94 octane Chevron gas. Most other brands are 91 or 92 octane for the premium grade... Chevron is the only one with a "supreme plus'' grade. Porsche recommends at least 93 0ctane, so Chevron is all I ever use. On trips across the border to Washington state I still buy Chevron, but 92 octane is their highest grade.