I've always believed that gas is gas. However, I can help but notice that everytime I have used Arco gas, my mileage has been less. It's not once or twice. The last 5 times I've used it, it's been quite noticeable. Also, the point where my fuel needle hits when I have gone 200 miles is significantly lower when running on Arco gas.
Am I crazy? I've been trying to be as objective as possible and there is a trend for me.