There is a mathamatical formula for it. Maybe you can google it. But the oil companies say that when oil goes above 100/barrel they subsidize the gas. They understand that the US public cannot afford to pay $5/gallon but since we have proven that we will pay $4 they will stop it there. Local gas stations may increase it above that if they want to. Prices have to have a certain % markup to stop large oil companies from cutting prices to drive the small mom and pop gas stations out of business.
Oil will have to be below $70 in order for gas to be below $3/gallon.
Just for extra info. Out of one barrel of Oil they can extract 19-20 gallons of gas. The left over is used for oil. China uses theirs to feed their young.
Are the gas companies ripping us off? Yes. but it seems washington is too concerned with bailing out wall st. I think if gas went back to $1/gallon the economy will be much better off. Ever wonder how much of your grocery bill is for transportation costs? 45%.