We got new Circle K with miles and it is TopTeir but I suspect it is all marketing when they claim better fuel mileage. I always ran Exxon with rare case of Shell but Circle K bought all Exxon stations and converted all but one to new miles so it is out of the way to go to Exxon. Do you trust Circle K in your vehicle now that they updated their fuel? Gas is 10 cents cheaper than the Shell across from it so about 2 bucks a tank which is also TopTeir and marketing as best for your vehicle. Very busy station as right on interstate. I ran one tank but they claim it takes 4 tanks to notice gain according to their website.