Triple A says the national average for regular unleaded fell 9 cents to $3.19 a gallon this week, while Oregon's average dropped 11 cents to $3.50 a gallon.
The Oregon average is the lowest it's been since mid March.
Triple A expects gas prices to keep falling due to relatively low demand and abundant supplies.
It could fall another 10 to 20 cents a gallon by the end of the year.