NEW YORK (CNNMoney.com) -- Gasoline prices fell Sunday, bringing down the nationwide average in a motorist group survey by more than 42 cents overall from a mid-July high.

The price of regular unleaded gasoline at the pump fell four-tenths of a cent to $3.688 a gallon, according to the Daily Fuel Gauge Report from motorist advocacy group AAA and the Oil Price Information Service. The average is based on credit card swipes at 100,000 service stations.

Prices have fallen 10.4% since hitting a record high of $4.114 a gallon on July 17.

The dip comes after U.S. crude for October delivery saw the largest drop in 17 years, closing down $6.59 to settle at $114.59 a barrel on the New York Mercantile Exchange.

Gas prices remain about 99 cents, or 33.7%, higher than a year ago.

State prices: Gasoline exceeded $4 a gallon in two states, Hawaii and Alaska, according to the survey. Alaska had the highest prices at $4.536 a gallon, down a penny from the previous day. Hawaii prices averaged $4.410, followed by Utah at $3.970, Idaho at $3.961 and California at $3.960.

Missouri had the cheapest gas, with prices falling to $3.443 a gallon. Prices in South Carolina were the second lowest at $3.457, followed by Tennessee at $3.484.

Ethanol: The price of E85, an 85% blend of corn-derived ethanol available to some vehicles, rose to $3.020 a gallon on average from $3.014, AAA reported. Ethanol burns cleaner than gasoline but has a lower energy content and burns less efficiently in flex fuel vehicles.

Diesel: The average price for diesel fuel, which is used in most trucks and commercial vehicles, fell by a penny to $4.305 a gallon from $4.311 the day before, according to AAA. The price of diesel has risen 47% over the past 12 months.

Because of its use in transporting goods, high priced diesel can help drive up the prices of products and services. Drivers in Hawaii, the state with the most expensive diesel, paid an average of $5.308 a gallon for diesel. Diesel was cheapest in Missouri, where prices fell to an average of $4.038.

Long term trends: Gas prices have dropped a little more than 15 cents in the past two weeks, the publisher of a national survey said Sunday.

The latest Lundberg Survey, carried out on Friday, found an average price of $3.70 for a gallon of self-serve regular.

The survey tallies prices at thousands of gas stations across the nation.

Publisher Trilby Lundberg attributed the fall to the drop in demand and the fact that gas refiners and retailers did not pass on higher expenses to their customers.

Because gas demand typically goes down in September, prices could continue to fall, Lundberg said

The city with the cheapest gas on average in the Lundberg Survey was St. Louis, Missouri, at $3.37. Drivers in Anchorage, Alaska, where the average price of gas was $4.34, paid the most.

Here are average prices of a gallon of self-serve regular in some other cities: