Another update: Gasoline prices declined recently, and are down about 8 cents nationally over the last 2 weeks. Brent crude spot prices increased to $117.48 per barrel two weeks ago, and then declined sharply to $108.49. However Brent has increased over the last few days to $113 per barrel.
We are still paying over $4 per gallon in California (I filled up on Friday and paid $4.15 per gallon.
Using the calculator from Professor Hamilton, and the current price of Brent crude oil, the national average should be around $3.67 per gallon. That is about 10 cents below the current level according to Gasbuddy.com