As summer comes to a close, so does the peak demand season for motor gasoline in the United States. Typically, gasoline prices weaken in the autumn months as demand for gasoline drops. Here are some supply and demand numbers from this summer and how this year compared to last year and years past.

We began summer 2010 (Memorial Day weekend) with nearly 219 million barrels of gasoline in inventories. This compared to 203 million in 2009, 209 million in 2008, 198 million in 2007, and 209 million in 2006.

We're finishing summer 2010 (Labor Day weekend) with 225.5 million barrels of gasoline available. This compares to 205 million in 2009, 194 million in 2008, 191 million in 2007, and 206 million in 2006.

Demand for motor gasoline during this summer averaged 9.35 million barrels per day. This compares to 2009 when demand averaged 9.18mbpd. In 2008, average demand was 9.37 million barrels per day, in 2007, the number was 9.60mbpd. You can see that as the economy collapsed, demand dropped. However, the economy has since improved slightly and demand is edging higher.

Looking at numbers provided by the Department of Transportation, miles driven across the country rose in May 2010 compared to 2009. Travel on all roads and streets changed by 0.1% (0.3 billion vehicle miles) for May 2010 as compared with May 2009. For June, the number compared to last year grew a large amount. Travel on all roads and streets changed by 1.3% (3.4 billion vehicle miles) for June 2010 as compared with June 2009.

When all this is said and done, supply for this time of year is the highest its been since records started being kept in 1990. I suspect that prices this autumn will move lower, especially in late-September and October as many areas usher in winter-spec gasoline.