It's not exactly uncommon to see diesel drop below gasoline in the summer (I hope I'm not just stating the obvious) With an exception for last summer, that's been the historical trend... Remember, we're talking national averages - your local values speak nothing to actual trends.
U.S. Gasoline and Diesel Retail Prices
The last time diesel was cheaper than gasoline was in July 2007. The time before then was July 2006 and the time before that was oddly, September 2005.
Just for fun, I just plotted the difference in price for gasoline v. diesel (all formulations of both).... There's a fairly nice cycle... Since '94, diesel has averaged 6 cents more than gasoline... Since 2000, that average is 9.2 cents. I'm curious to see what happens in the next couple years - it looks like it's stabilizing, but we can't predict the future
