Gas prices falling due to winter blend gasoline

Autumn is finally here, and the kids are finally back in school.  Of course, autumn has the more familiar name of “fall,” as we begin the transition from long, warm days to less sunlight and less heat.  The leaves on the trees and the daytime temperatures aren’t the only things falling.  While they are still higher than the historical average, gas prices in the US are falling once again!

Throughout the month of September, the average price of a gallon of gas has dropped about 6 ½ cents.  As of September 24, the national average is about $3.48, a good 31 cents lower than this time last year.  Some industry experts believe prices will continue to drop over the next few months, and in many areas, they may fall below $3.00 per gallon for the first time since 2010.  Charleston, South Carolina, currently has the lowest average price of around $3.09.

Newer drivers, like me, rejoice whenever gas prices go down.  Buying gasoline is something that can eat up my limited budget, so it will be nice to save a couple of dollars every time I fill up in the next few months.  However, more experienced drivers are aware that it is normal for gas prices to fall in the fall.  AAA spokesperson Mark Jenkins noted:  “The summer driving season is over, demand is down, and refineries are switching to the cheaper winter-blend gasoline.”

That’s right.  Summer gasoline and winter gasoline have slightly different makeups.  Since temperatures are hotter in the summer, gasoline needs to have less vapor pressure to prevent boiling and evaporation.  To throw some numbers in, standard atmospheric pressure is about 14.7 pounds per square inch (PSI); EPA standards for summer-blend gasoline mandate that its vapor pressure not exceed 9.0 PSI.  For the winter, however, atmospheric temperatures are lower, and gasoline vapor pressure standards vary from 11 PSI (September-December) to about 13.5 PSI (January-March).  Winter-blend gasoline has more butane, and this readily available gas makes the winter blend cheaper to make than summer-blend.  Winter-blend gasoline began rolling into stations on September 15.  In essence, gasoline prices should always be falling at this time of year.

While the winter blend gasoline is cheaper, it is more susceptible to evaporation and causing engine backfires.  As a result, this also means lower gas mileage.  With my car, for example, I am used to a routine.  Its gasoline tank carries 13 gallons, and I get about 30 miles per gallon.  In the summer, I could usually run it down to a quarter-tank of gas (between 270 and 300 miles) before having to refill.  In the winter, however, I may find myself needing to fill up every time the tank goes to half-full, and this might just be after 180 miles or so of driving.  Potentially, this could mean more trips to the gas station.

Gasoline prices should continue to drop as the temperature drops.  Prices in the Raleigh/Durham area are about 10 cents cheaper than they were in August.  However, because of more additives in the winter, I might be getting lower gas mileage, and I might not really be saving much at all.  Oh, the joys of being an adult!

David Pilley

David Pilley

David Pilley is a May 2010 graduate of the University of North Carolina at Chapel Hill, with a B.A. in communication studies and a creative writing minor. He is a native of Raleigh, North Carolina.

He played clarinet for the Marching Tar Heels in 2005 and 2006. He also volunteered for STV, the student-run television station at UNC-Chapel Hill, in the spring of 2010. He shot video, wrote scripts, and acted for “Off the Cuff,” UNC’s longest running sketch comedy show. He has the rare distinction of having lived in a dorm all four years of his undergraduate college career. He was also on Franklin Street on the night of April 4, 2009. His future plans are to pursue a master’s degree in journalism and to one day work for the media as a sports journalist or broadcaster.

Being one of eight children, David realizes finance is an important topic to everyone, regardless of his/her knowledge of the subject. His interests are in personal finance, budgeting, and savings.

In his spare time, David enjoys watching sports and standup comedy, as well as doing crossword puzzles and writing in the first person. He also thoroughly enjoys trivia and, one day, hopes to participate on the game show Jeopardy!, where he will try to break Ken Jennings’ 74-game win streak.
David Pilley

Latest posts by David Pilley (see all)