Fuel prices fall for 14th day in a row
Retail gasoline prices have fallen more than 20 cents a gallon since July 16, a level not seen since late May.
NEW YORK (CNNMoney.com) -- Fuel prices fell for the 14th straight day, with gasoline approaching $3.90 a gallon, a daily survey of gas station credit card swipes showed Thursday.
Gasoline: The nationwide average price of regular unleaded gas fell 1.7 cents to $3.909 a gallon, a level not seen since late May, according to a nationwide survey from motorist advocacy group AAA.
The average price for regular has fallen more than 20 cents since hitting a record high of $4.114 at the pump on July 16, where they stayed for two days, according to AAA data.
Gas prices have been following a decline in oil prices, which have been driven lower by worries that pricey fuel is slowing demand.
Ethanol: High gas prices have caused many drivers, particularly those in regions with strong agricultural industries such as the Midwest, to switch to ethanol as their fuel of choice.
The price of E85, an 85% ethanol blend which burns cleaner than straight gasoline and is made primarily from corn, fell 1.1 cents to $3.155 a gallon on average, AAA reported.
While ethanol is derived from renewable sources, it is less efficient than gasoline. As a result, a car running on E85 would pay the equivalent of $4.151 per gallon to get the same mileage as gas, the AAA survey estimated.
Diesel: The average price of diesel fuel, which is used to power most trucks and commercial vehicles, fell to $4.698 a gallon from $4.714, according to AAA.
Diesel prices have climbed more than 59% in the last 12 months. And because diesel is used to transport goods, the high prices have affected the prices of other items.
State prices: The AAA survey averages data from credit card swipes at 85,000 fuel stations around the country, and gas remains above $4 a gallon in 13 states.
Gas in Alaska, the state with the highest prices, fell to an average of $4.636 a gallon from $4.648 the previous day. Hawaii, the state with the second highest prices, saw average prices rise slightly to $4.507. California, the state in third place, saw prices slip to $4.266 on average, the AAA survey said.
Drivers in Oklahoma, the state with the cheapest gas, saw prices fall to $3.636 from $3.655 a gallon the day before. In Minnesota, the next cheapest state for gas, drivers paid $3.655 on average, followed by Ohio at $3.669.
Drivers in Hawaii, the state with the most expensive diesel, saw diesel prices rise to $5.409 a gallon. Diesel was cheapest in Oklahoma at $4.473, according to the AAA survey. 
