While mogas and crude have a high degree of correlation (since it takes crude to make gas), the refining margin and pump price have their own supply/demand situations.

This spring, there was an unprecedented fear/hype that we'd run out of mogas this summer.  The gas/crude spread hit $15-16/bbl or 35 cts.  Typical winter time value is $3/bbl and maybe $7/8 in the summer.  So we had $8/bbl(say 20 cts) to drop on gas just to get to a normal summer price relative to crude.

The summer gas season didn't have any big supply disruptions so price has faded down to more typical levels.  API/DOE stock levels are more than sufficient and rising instead of falling which is more typical for gas in summer.

Also, after Sept 1 mogas demand starts to drop (end of vacation season).  Speculators and wholesalers will have to lose the extra length they've been holding as insurance.  They also like to lower tank levels as the RVP change for winter starts passing through the system.  (Winter gas is more volatile than summer so that cars will start in cold weather).

Others point out that pump prices are quick to rise and slow to fade.  That's the nature of a not too competitive market.  Dealers hate to lose $ on existing stocks but are all too happy to take a quick markup.