The following is a copy of a simple tri-fold brochure that Audi has begun placing in all new cars. Very simply, it describes which brands of gas are TOP TIER-rated gasolines. Clients often ask me about placing additives in their gasoline...Audi's answers is to use one of the gasoline suppliers listed in the brochure, and you should not need to add anything, yourself, to your gas. Below is an excerpt from www.toptiergas.com. After that, I copied the Audi brochure, both sides, for you...
Top Tier Detergent Gasoline
TOP TIER Detergent Gasoline is the premier standard for gasoline performance. Six of the world's top automakers, BMW, General Motors, Honda, Toyota, Volkswagen and Audi recognize that the current EPA minimum detergent requirements do not go far enough to ensure optimal engine performance.
Since the minimum additive performance standards were first established by EPA in 1995, most gasoline marketers have actually reduced the concentration level of detergent additive in their gasoline by up to 50%. As a result, the ability of a vehicle to maintain stringent Tier 2 emission standards have been hampered, leading to engine deposits which can have a big impact on in-use emissions and driver satisfaction.
These automakers have raised the bar. TOP TIER Detergent Gasoline help drivers avoid lower quality gasoline which can leave deposits on critical engine parts, which reduces engine performance. That's something both drivers and automakers want to avoid.
Here's the brochure: