Price of gas in San Diego... on Coronado Island (just the 2 gas stations, no others I know of) This year vs last year

For perspective, this next one is from last Memorial Day (May 2007): http://justacarguy.blogspot.com/2007/05/price-on-coronado-island-in-middle-of.html#links



I bet they have no explanation (that will make sense) why the cheap stuff is up 40 cents, but the expensive stuff is up only 20 cents.