I second that.. I've had my 2014 ghibli SQ4 for 7 mos. now & have tried premium & regular and I don't see any difference in performance, except my exhaust smell is a lot stronger with the premium. And I've had no knocking issues whatsoever. My car has around 73,000 miles on it, & its my daily driver. Thanks.Been using 89 octane (plus) for 9,000 miles. More power than I need and highway mileage is 26-28 with no problems. Lately been putting in 91 octane sometimes since it's so cheap but no noticeable difference in performance. I think 93 is simply a waste of money with no benefits. But use whatever you think works and be happy!