I have a lincoln ls 2002 v6 3.0L. What gas should I use? 91 or 93? I've used 87 and mu car sputters and skips and it not the coils or plugs and my e light isn't on so do u think its the 87 thatsa makin my car do that? And can I use 93 octane although it calls for 91? I know 87 is a no no