According to Gasbuddy.com (see graph at bottom), gasoline prices are down slightly over the last few days to a national average of $3.66 per gallon. One year ago for the week of Memorial Day, prices were at $3.67 per gallon, and for the same week two years ago prices were $3.85 per gallon.
According to Bloomberg, WTI oil is at $94.15 per barrel, and Brent is at $102.64 per barrel. Last year on Memorial Day, Brent was at $107.86 per barrel, and two years ago Brent was at $114.85.
Using the calculator from Professor Hamilton, and the current price of Brent crude oil, the national average should be around $3.40 per gallon. That is about 26 cents below the current level according to Gasbuddy.com, however I think there is a seasonal factor that isn't included in the calculator.