What is summer-blend gas?

Answers to your questions about the news.
April 12 2004 5:55 PM

What Is Summer-Blend Gas?

And if it's so clean, why don't we use it year-round?

According to a survey of 8,000 service stations released yesterday, American motorists are paying an average of $1.80 for a gallon of gas. While several factors—including record demand and the unusually high cost of crude oil—account for the increases, news reports also place some blame on shortages caused by the annual switch to smog-reducing "summer blend" gasoline. What is summer-blend gas? And if it's so clean, why don't we use it year-round?

The term "summer blend" is shorthand for a menu of federally and locally mandated summertime fuel recipes that are designed to cut down on smog. The gasoline we use is always refined from an intricate blend of ingredients; the process combines coffee-dark crude oil with various additives that increase performance or make fuel burn more cleanly. Because overlapping federal and local requirements call for different recipes in different locales and seasons, there are approximately 20 distinct "boutique blends" of gasoline sold in the United States. Some Americans end up pumping a blend called Carb (named for the California Air Resources Board) while others burn Atlanta (named for Georgia's capital, where it's sold).

Refineries brew their summer blends by removing hydrocarbons that are more prone to evaporate in hot weather. These chemicals, called volatile organic compounds, react with airborne pollutants in the summer sun to form ozone, one of the main components of smog. From June 1 to Sept. 15, the EPA mandates that pumps in 12 high-ozone urban areas—such as Los Angeles, New York City, and Baton Rouge—deliver gasoline that meets special low-evaporation standards. Several states have voluntarily adopted the rules, and 15 have enacted their own seasonal-blend regulations on top of the EPA's. For example, pollution-conscious California has mandated that service stations must start selling its summer blend in May.

Summer-blend gas isn't new. It was first sold in 1995, as required by the Clean Air Act's 1990 amendments, and the current, even cleaner, concoction was phased in for the summer of 2000. Since then, there have been sharp spikes in fuel prices every spring as summer blends get rolled out. This is not so much because it's expensive to make the gas—the added cost per gallon is only 1 or 2 cents—but because refineries generally try to sell every last bit of winter fuel before mixing in the slightly more expensive summer batch. Sometimes they draw down the stock too far, creating shortages before the first deliveries of summer blend enter the supply chain. The return to normal blends in the fall causes a far less pronounced spike because the industry, free from summer standards, doesn't bother selling off the summer gas before mixing in the less pricey stuff.

So why not use the summer blend year-round? The main reason—apart from the fact that the 1990 law isn't written that way—is that summer-blend gas doesn't work as well in the winter. Summer blend's low-evaporation rate makes engines less likely to stall in hot weather but can make them difficult to start in the cold.

Explainer thanks Richard A. Gilbert of University of California-Berkeley, John Millett of the Environmental Protection Agency, and Jim Williams of the American Petroleum Institute.

TODAY IN SLATE

Politics

The Democrats’ War at Home

How can the president’s party defend itself from the president’s foreign policy blunders?

Congress’ Public Shaming of the Secret Service Was Political Grandstanding at Its Best

Michigan’s Tradition of Football “Toughness” Needs to Go—Starting With Coach Hoke

Windows 8 Was So Bad That Microsoft Will Skip Straight to Windows 10

Homeland Is Good Again! For Now.

Politics

Cringing. Ducking. Mumbling.

How GOP candidates react whenever someone brings up reproductive rights or gay marriage.

Building a Better Workplace

You Deserve a Pre-cation

The smartest job perk you’ve never heard of.

The Ludicrous Claims Women Are Pitched at “Egg Freezing Parties”

Piper Kerman on Why She Dressed Like a Hitchcock Heroine for Her Prison Sentencing

Behold
Oct. 1 2014 11:48 AM An Up-Close Look at the U.S.–Mexico Border
  News & Politics
The World
Oct. 1 2014 12:20 PM Don’t Expect Hong Kong’s Protests to Spread to the Mainland
  Business
Business Insider
Oct. 1 2014 12:21 PM How One Entrepreneur Is Transforming Blood Testing
  Life
The Eye
Oct. 1 2014 1:04 PM An Architectural Crusade Against the Tyranny of Straight Lines
  Double X
The XX Factor
Oct. 1 2014 1:01 PM Can Activists Save Reyhaneh Jabbari?  
  Slate Plus
Behind the Scenes
Oct. 1 2014 10:54 AM “I Need a Pair of Pants That Won’t Bore Me to Death” Troy Patterson talks about looking sharp, flat-top fades, and being Slate’s Gentleman Scholar.
  Arts
Behold
Oct. 1 2014 1:04 PM The Many Faces of Texas
  Technology
Future Tense
Oct. 1 2014 11:48 AM Watch a Crowd Go Wild When Steve Jobs Moves a Laptop in This 1999 Demonstration of WiFi
  Health & Science
Bad Astronomy
Oct. 1 2014 12:01 PM Rocky Snow
  Sports
Sports Nut
Sept. 30 2014 5:54 PM Goodbye, Tough Guy It’s time for Michigan to fire its toughness-obsessed coach, Brady Hoke.