To become a Top Tier gasoline supplier, the petroleum company or fuel marketer must submit their gasoline detergent additive to GM for testing at a certain dose. The applicant must sign a pledge to use that additive and dose for at least one year.
I find the one year part interesting. A company could use the additives to qualify for top tier status and then stop using them after a year to reduce costs without losing the status. My opinion is that it is marketing hype.