A drop in refinery utilization tightened gasoline supplies and caused nearly half of all state price averages to increase for the week ending Oct. 21, as the national average increased 1 cent to $2.64 per gallon, according to AAA.

Refinery utilization reached 83%, which was the lowest level since September 2017. As a result 22 states saw price increases, while 19 states saw gasoline prices decrease and 10 held steady. Washington, D.C. was included in the list.

The current national price is 2 cents higher than a month ago and 21 cents less than a year ago.

"Peak refinery maintenance season has caused volatility across the country," said Jeanette Casselano, AAA spokesperson. "Motorists can expect fluctuations at the pump likely through the end of the month due to ongoing maintenance and tighter gasoline supply."

States with the most expensive gasoline now include California ($4.14), Hawaii ($3.64), Nevada ($3.44), Washington ($3.40), Oregon ($3.33), Alaska ($3.07), Arizona ($2.90), Idaho ($2.84), Pennsylvania ($2.75), and Utah ($2.74).

States with the largest weekly price increases include Kentucky (10 cents), Oregon (7 cents), Idaho (6 cents), Delaware (6 cents), South Carolina (6 cents), Michigan (6 cents), Alaska (5 cents), Washington (5 cents) and Florida (4 cents).