Gas: Under $4 a gallon and falling
Fuel prices decline for 11th consecutive day.
NEW YORK (CNNMoney.com) -- Gas prices declined for the 11th straight day on Monday, falling to a level not seen since May, according to a nationwide survey of filling station credit card swipes. Other fuel prices also continued to fall.
Gasoline: The price of regular unleaded gasoline at the pump slipped 1.2 cents to $3.958 a gallon on average, a daily survey from motorist advocacy group AAA revealed.
A second report from Lundberg Survey, Inc. showed that gasoline prices had slipped 12 cents over the past two weeks to an average of $3.9959 a gallon.
The latest Lundberg survey was conducted on July 25th.
High fuel prices have strained on American consumers and businesses, making transportation and shipping more expensive.
Average gasoline prices first crossed the $4 mark on June 7 when they hit $4.005 a gallon, according to the AAA survey. Prices rose to $3.952 a gallon on May 29 and continued to trend upward to a record high of $4.114 on July 16.
Prices stayed there for two days before beginning their retreat, following a double-digit decline in oil as investors worried that the high cost of fuel was leading to a slowdown in demand.
Ethanol: High fuel prices have caused many drivers, particularly those in states with strong agricultural industries, to switch to ethanol as their fuel of choice.
The price of E85, an 85% ethanol blend, which burns cleaner than pure gasoline and is made primarily from corn, fell 1.8 cents to $3.222 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 $4.24 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 $4.736 a gallon from $4.748, according to the AAA survey.
Diesel remained more than 60% higher than last year. And because of its use in transporting goods, high prices for diesel have affected the prices of other items.
Local prices: The AAA survey averages data from credit card swipes at 85,000 fuel stations around the country. The survey found that the number of states that suffer from gas prices above $4 a gallon fell to 14 on Friday.
Gas in Alaska, the state with the highest prices, fell to $4.643 a gallon from $4.68 last week Friday, according to AAA. The Lundberg survey, which measures gas prices by city, found the highest urban gas prices in Anchorage, Alaska at $4.43.
Hawaii, the state with the second highest prices, saw average prices fall to $4.479. California prices dipped to $4.316 on average, the AAA survey said.
Drivers in Oklahoma, the state with the cheapest gas, saw prices fall to $3.686 from $3.769 a gallon on Friday, AAA said. In Minnesota, the next cheapest state for gas, drivers paid $3.714 on average, followed by Ohio at $3.73.
Lundberg found the cheapest gas in Wichita, Kan. at $3.61 a gallon.
Drivers in Hawaii, the state with the most expensive diesel, saw prices fall to $5.372 a gallon, while diesel was cheapest in Oklahoma at $4.51, according to the AAA survey. 
