ARCO gasoline is one of the least expensive gas brands ... except Kirkland Gas at Costco. But I cannot always get to Costco. So I decided to fill up with ARCO but I know ARCO gas does not contain any engine cleaning (I do not know if we need one). So, I decided to purchase STP gas treatment for $2.99 (plus tax) to put it in.

Even with this extra, it is cheaper than buying gas at Chevron, Shell or Texaco.