A good explanation of the factors that determine gas prices.
Crude oil prices contribute the most
Considering there are 42 gallons per barrel price:
$100 per barrel = $2.38 of the pump price
$70 per barrel = $1.67 of the pump price
$40 per barrel = $0.95 of the pump price
Refineries add approximately 65¢ per gallon
Federal tax is 18.4¢ per gallon (since 1993)
State tax varies, but averages around 30¢ per gallon
Transportation and retail operations can contribute to between 20¢-50¢ per gallon with approximately 15¢ of that going towards station operating revenue