We drove a 1996 Chevrolet for a very long time. We did have problems with gasoline leaks. I knew where to place the blame. I believe 1998 and newer cars in the US were updated to operate on oxygenated fuel. I might say a lot more, but it would only be my opinion.
When my XS650 was new, leaded fuel was only available in "REGULAR" grade. The owners manual states 91 octane LEADED. I don't recall it elaborating the rating method though we had long been using (R+M)/2. Back then I filled the tank halfway with LEADED fuel and finished with PREMIUM. Today, I seem to have no issue with 87 octane E0.
