Cleaner-Burning Gasoline: An Update

This page last reviewed September 25, 2008

Since 1996, California gasoline has been the cleanest in the world. California’s cleaner-burning gasoline regulation is one of the cornerstones of the state’s efforts to reduce air pollution and attain healthful air quality for all Californians. This fact sheet contains the latest information on cleaner-burning gasoline.
What is cleaner-burning gasoline?
Cleaner-burning gasoline is fuel that meets requirements established by the Air Resources Board (ARB). All gasoline sold in California for use in motor vehicles must meet these requirements, which have been in effect since Spring 1996. Cleaner-burning gasoline reduces smog-forming emissions from motor vehicles by 15 percent and reduces cancer risk from exposure to motor vehicle toxics by about 40 percent.
There are eight basic specifications for cleaner-burning gasoline. They are:


Reduced sulfur content. Sulfur inhibits the effectiveness of catalytic converters. Cleaner-burning gasoline enables catalytic converters to work more effectively and further reduce tailpipe emissions.


Reduced benzene content. Benzene is known to cause cancer in humans. Cleaner-burning gasoline has about one-half the benzene of earlier gasoline, thus reducing cancer risks.


Reduced levels of aromatic hydrocarbons, which react readily with other pollutants
to form smog.


Reduced levels of olefins, which also react readily with other pollutants to form smog.


Reduced vapor pressure, which ensures that gasoline evaporates less readily.


Two specifications for reduced distillation temperatures, which ensure the gasoline burns more completely.


(See Number 6.)


Use of an oxygen-containing additive, such as MTBE or ethanol, which also helps the gasoline burn more cleanly.
ARB regulations allow refiners to vary from many of these requirements as long as they can demonstrate, using ARB-approved procedures, that the fuel provides comparable air-quality benefits. Several refiners have used these regulations to make cleaner-burning gasoline without MTBE or other oxygenated additives. The pending elimination of MTBE use in California is explained in a companion fact sheet, "Cleaner-Burning Gasoline Without MTBE."
Cleaner-Burning Gasoline Has Been Effective
An independent study by the University of California, Berkeley found a decrease in motor vehicle emissions following cleaner-burning gasoline’s introduction in Spring 1996. ARB analyses of weather data and air pollution levels also indicate that the use of cleaner-burning gasoline has reduced peak smog levels. Benzene levels in California’s air decreased by approximately 50 percent in 1996 following the gasoline’s introduction.
ARB regulations require motor vehicles to meet increasingly cleaner emission standards every year through 2010. To meet those requirements, vehicle manufacturers are designing low-emission vehicles that take full advantage of cleaner-burning gasoline’s properties. Cleaner-burning gasoline will help tomorrow’s vehicles reduce air pollution even further.
Air-Quality Benefits At A Reasonable Cost
Cleaner-burning gasoline costs from 5 to 15 cents more per gallon to produce than conventional gasoline. Gasoline production costs are one of a number of factors that determine gasoline prices at any given time. Other important factors include crude-oil prices, weather conditions, and seasonal supply and demand. Gas prices change continuously in response to these and other factors.
The California Energy Commission estimates that, on average, the use of cleaner-burning gasoline has added 5 to 8 cents a gallon to gasoline prices since 1996. When the added fuel costs are compared to the significant decrease in vehicle emissions, cleaner-burning gasoline is shown to be an extremely cost-effective way to reduce air pollution.
Dealing With Fuel Emergencies
In normal circumstances, California’s refineries make all or nearly all of the gasoline used in the State. Out-of-state refineries typically produce small amounts of cleaner-burning gasoline for sale in California. However, a refinery breakdown or other emergency can produce a situation where in-state production of gasoline is less than consumer demand.
A refiner that has experienced a breakdown or other unforeseen emergency can ask ARB for a variance to temporarily sell non-complying gasoline in California. By issuing a variance, ARB can enable a refiner to obtain sufficient gasoline to prevent a fuel shortage. ARB issued its first-ever gasoline variance in July 1999 to Chevron Products Company following an accident at Chevron’s Richmond refinery.
ARB did not receive variance requests after refinery accidents in 1996 and Spring 1999. In those cases, increased imports of cleaner-burning gasoline from out-of-state refineries helped prevent any acute gasoline shortages.
U.S. Gas To Become More Like California Gas
Since 1995, the U.S. Environmental Protection Agency has required the nation’s smoggiest metropolitan areas to use reformulated gasoline that provides about one-half the air-quality benefits of California’s cleaner-burning gasoline. In 2000, U.S. EPA required those areas to use cleaner gasoline that provides most but not all of the benefits of California gasoline. In addition, U.S. EPA plans to implement low-sulfur requirements that will bring gasoline in the rest of the nation closer to California standards.

California Gasoline Program