I have a 300 Sel that I run Sunoco 94 octane gas in. Sometimes I can only get 91 or 92 octane when I am out of town where there are no Sunoco's. When I burn the lower octanes (91 or 92) My car works bad. Skips when I first start up for a second or two. I have tried putting in a bottle of octane boost but does not make a differance. As soon as I fill with 94 it works perfect. This is not making sense to me. There has to be another reason for this. Any ideas? I know everone that has a Mercedes does not run Sunoco gas. The car is a low miler 60k 1990, all new plugs wires cap and so forth. Could it be timing or wrong plugs? Any help would be great, I know someone out there has the answer. Thanks