Higher oil prices are to blame for rising gasoline costs, according to AAA.

AAA said the national gas price average for the week of Oct. 8 was $2.91, up 3 cents from last week and six cents more per gallon than a month ago.

“The September switch-over to winter-blend gasoline ushered in cheaper gas prices compared to the summer, but that drop was short lived,” said Jeanette Casselano, AAA spokesperson. “Crude oil accounts for half of the retail pump price and crude is selling at some of the highest price points in four years. That means fall and year-end prices are going to be unseasonably expensive.”

AAA said regional refinery maintenance also is contributing to higher pump prices.

Indiana saw one of the sharpest increases nationally when compared to last week’s prices. The average price for gasoline in Indiana the week of Oct. 8 was $2.92, up 7 cents from last week. 

Crude oil has priced higher amid concerns of global crude supply and geopolitical tensions, including pending sanctions with Iran and Venezuela’s unstable economy. AAA said average fall gasoline prices nationally are at its highest levels since 2014.

Crude oil is selling at $25 per barrel higher than a year ago and was selling at $75 per barrel last week, AAA said.