(Portland, OR) -- Gas prices in Oregon continue to decline. Triple-A reports Oregon's average fell two cents over the last week to three-94 a gallon. The national average was unchanged at three-50. The national average didn't decline, because of a spike in gas prices in the Great Lakes states. A refinery in Illinois went offline earlier this month when a tornado damaged the power supply, and that sent gas prices soaring. When that refinery resumes production, the national average price for gas should continue its decline.