They sponsored a study, found that Top Tier made major reduction in deposits. Here are their conclusions:
"1. The test engine operated on a TOP TIER gasoline averaged 19 times fewer intake valve deposits than when it was operated on non- TOP TIER gasoline. (based on the ASTM D6201 test - TOP TIER gasoline averaged 34.1mg of deposits per intake valve versus non- TOP TIER average of 660.6mg)
Based upon secondary research findings, long-term use of a gasoline without an enhanced additive package can lead to reductions in fuel economy of 2-4%, drivability issues, and increased emissions.
In most cases, carbon deposits can be reduced or removed from critical engine components1 by switching to a gasoline that meets TOP TIER standards.
Approximately six in ten drivers (63%) believe there is a difference in the quality of gasoline sold by retailers, yet only (12%) of drivers purchase gasoline based upon its detergent additive package. The primary motivation for choosing a particular gas station is location / convenience (75%), followed closely by the price of the fuel (73%).
Most TOP TIER gasolines do not cost significantly more than non-TOP TIER gasoline. The average price difference between the TOP TIER and non-TOP TIER brands surveyed was three cents per gallon over a 12-month period."