Mine is at 19.5 in mixed driving. Still on the dealer tank and currently 265 miles on the odometer. Not 100% sure which octane they put in but when the subject came up at the dealership, I asked what they were putting in it. The salesman said, "it is an ST, has to have 93...". Maybe he didn't know 87 was sufficient?? If I had to put money on it, I'd bet it was just 87.