I just bought some ARCO from my local station and now they have a new sign stating " smile you bought TOP TIER gas for less". Gee wiz that California list is getting rather large.
I've heard an estimate that the additional cost of a detergent package (compared to minimum EPA standards) that meets Top Tier standards plus the licensing fee might be in the range of 1 or 2 cents per gallon. If it improves sales, it would be well worth it.
I remember seeing the typical "treat rate" for one detergent package that was already Top Tier qualified. Any fuel marketer that wanted to use it could just buy it and use the pre-qualified test reports from the additive maker. I think it was something like a 1:1700 treat rate. Costco's "Kirkland Signature" (formerly Clean Power) setup involves an additive tank on-site where the additive is delivered by tanker. The majority of locations use an underground additive tank with about a 1500 gallon capacity. I think for most locations this should last at least 6 months. In the grand scheme of things, additives don't really cost that much to the fuel marketer, but can yield big returns if it can be advertised.
I understand some people are cynical that "Top Tier" is some money-making scheme from the licensing company. However, my understanding is that it was created by several automakers, who were having issues because of inadequate detergent levels in fuel along with the inevitable warranty issues. Part of the issue was that the EPA mandated a minimum level of detergent performance, and supposedly some gasoline marketers were actually dialing down the level of detergent additive as a result. Fine for some generics, but they were recommending some brands by name because they were providing high detergent levels.