No, I'm asserting that your graph of crude futures is irrelevant because it does nothing to refute the fact that gasoline prices are seasonal.
In the late summer, demand for gasoline declines because people drive less, and refiners begin to refine less gasoline and start building inventories of heating oil for the winter months. The reverse is true when the weather warms in the spring. People stop heating their homes, and drive more, so refiners refine more crude into gasoline and less into heating oil. These seasonal fluctuations may or may not change the seasonal demand for crude itself. That's one reason crude prices don't track the same seasonal path as gasoline prices. Of course, rising or falling crude prices can counteract or add to the seasonal trend of gasoline prices.
If you still think gasoline prices aren't seasonal, try your ten-year chart trick with them. (I did like the chart trick.)
D