Mine would turn over, no start. Three times. On the fourth time it fired up and stumbled its way to cold idle (~2150 RPM) and then settled in at a smooth 1900 RPM. Each time after the original start, i would wait for the fuel pump to cycle, but it didn't seem to help. Dealer said it stored no codes, and of course couldn't duplicate the problem. One tank of 93 with the Seafoam made it run like a champ. I've noticed a little better gas mileage too compared to before I ran that tank. And yes, even after switching back to 87, the mileage is still 2mpg better. My thought is that these cars obviously are sitting on the lot, not being run for a while. Moisture, and any traces of chemicals and seealants from assembly of the fuel system could be making it hard for these things to get fuel when the block is cold. I don't really know, I'm just guessing. But it would explain why my method is working (at least for now). I have probably put about 5 or more tanks of 87 with no extra additives since, so the solution is pretty long term.