The Clean Air Act of 1990 has impacted the gasoline markets of the Uni
ted Stales. Additives and reformulated gasoline have already been impl
emented in some cases to comply with regulations and emission standard
s, and gasoline will continue to be reformulated The regulations for r
eformulated gasoline have been divided into Phases I and II, starting
in 1995 and 2000, respectively, the second phase having more stringent
requirements. phase I is divided into two compliance models-Simple an
d Complex. These models are designed to facilitate the determination o
f fuel formulation compliance without the expense of extensive testing
of motor performance. The Simple Model can be used from 1995 to 1997,
and the Complex Model from 1997 on. Diesel fuels are also impacted by
the Clean Air Act. Other programs-such as CO oxygenate and California
Phase 2-have been initiated in response to air quality issues.