Issue: Sulfur odor detected in many vehicles today

Root Cause: The High Sulfur Content of Gasoline

The vehicle is not the cause of the sulfur odor. Crude oil, which gasoline is made of, has a very high sulfur content. During the refining process, not all of the sulfur is removed. In fact, 90% of all gasoline sold in the U.S. has a sulfur content of as much as 600 ppm (parts per million) an amount that significantly exceeds the 40 ppm levels that today's highly efficient vehicles emissions systems are designed to operate with.

How it Happens:

On vehicles with older or weaker emission systems, sulfur will normally mix with, and be absorbed by other gasses and compounds (eg. oxides of nitrogen) and is not normally detected. However, due to the introduction of more efficient emission systems, the catalytic converters will "scrub" or clean the exhaust gasses, converting these so-called "greenhouse gasses," like Co NoX and HC into harmless gasses, such as CO2. This process leaves the catalytic converter without any gasses to help absorb the sulfur, resulting in the release of a more sulfur-rich odorous gas.

When it Happens:

An odor can sometimes be detected while driving a car, but usually is caused not by the subject vehicle, itself, but by the lingering gasses from either a passing vehicle or a vehicle somewhere in front of the subject vehicle. These lingering gasses are drawn into the subject vehicle through the heating and ventilation system. In addition, sometimes the catalytic converter of the vehicle will purge itself of the sulfur, releasing an odor, usually after a period of hard acceleration. This is not normally detected while driving in the vehicle because the odorous gas exits the tailpipe at the rear of the vehicle and is left behing as the vehicle drives on.

The odor can sometimes be detected after parking the vehicle, particularly in confined spaces, such as a garage.

The Good News:

So far, the Pennsylvania Department of Environmental Protection has announced that 5 counties in Pennsylvania have opted to use re-formulated gasoline (RFG), which meets the strictest emmission laws, conforms to the ideal sulfur levels of 40 ppm, and is the only gasoline for sale in California.

RFG can usually be identified by a sticker on the gas pump. Exxon is one known distributor to market RFG.

Sources:

"Study on the effects of fuel sulfur on low emmission vehicles critaria pollutants" By American Automobile Manufactures Association (AAMA)

EPA Tier 2 status report and Tier 2 study, White paper

"What is RFG FAQ Report" by California Air Resources Board (CARB)

"Study on Composition of Gasoline" by Ohio State University