Gas prices down 21 days in a row
The national average price for a gallon of gas slips to $3.849. Only 10 states are above $4 a gallon.
NEW YORK (CNNMoney.com) -- Retail gasoline prices fell more than a penny overnight, extending a downward trend for the 21st straight day, a survey of gas station credit card swipes showed Thursday.
The national average price for a gallon of regular gas fell to $3.849 from $3.862 the previous day. That's down more than 6% from the record high of $4.114 that gas prices hit on July 16.
Gas prices have eased substantially in recent weeks amid signs that global demand for petroleum products is slowing.
But gas prices remain high in historical terms. Thursday's national average price is more than $1 higher than it was a year ago.
Ethanol. High gas prices have prompted many Americans to use alternative fuels like ethanol.
The price of E85, an 85% ethanol blend that burns cleaner than straight gasoline, fell 2 cents to $3.111 a gallon on average, AAA reported.
Ethanol, which is made from renewable resources like corn, is thought to be more sustainable than gas, but it is less efficient.
As a result, a car that burns E85 would actually pay $4.093 a gallon to get the same mileage as a car that runs on gas, according to AAA.
Diesel. The national average price for diesel fuel, used mostly for transportation and industrial purposes, fell to $4.614 a gallon from $4.633 the day before.
Diesel prices are up more than 56% over last year, which has contributed to a sharp increase in the prices that consumers pay for goods and services.
State prices. Based on data from credit card swipes at 85,000 fuel stations around the country, the AAA survey showed that gas remains above $4 a gallon in 10 states. That's down from 11 states and the District of Columbia in Wednesday's survey.
In Alaska, the state with the highest prices, drivers pay an average of $4.624 a gallon. Hawaii, the state with the second highest prices, saw average prices rise slightly to $4.476 from $4.468. California, the state in third place, saw prices slip to $4.177 on average.
Oklahoma remains the state with the lowest gas prices. The average price in the state is $3.609 a gallon. In Missouri, the next cheapest state for gas, drivers paid $3.617 on average, followed by Minnesota at $3.630 a gallon. 
