Dont want to clog up the spotting thread
http://www.toptiergas.com
Apparently BMW, General Motors, Honda, Toyota, Volkswagen and Audi weren't satisfied with the way many gas companies were reducing the detergent content of their gasolines, presumably to save costs.
To quote their purpose in forming Top Tier Gasoline:
"The intention of the TOP TIER Detergent Gasoline standards is to create a winning situation for gasoline, auto manufacturers and drivers. Currently, many gasoline retailers provide fuels with lower-quality additive packages that can build up deposits on fuel injectors and on intake valves. Others can build up deposits in
important chambers and may lead to intake valve sticking. These lower levels of additives can have negative impacts on engine performance and vehicle responsiveness."
Their standards for gasoline to meet (developed by BMW, General Motors, Honda, and Toyota) are listed there, as are retailers that meet the standards.
Long Story short, I tried sams club gas one time and I got a CEL for a new Fuel Pump ROFL (Not the FRS)