Gasoline prices in Maine rose 5.7 cents per gallon in the past week, averaging $2.52 a gallon on Sunday, according to GasBuddy’s daily survey of 1,228 gas outlets in the state.

Blame it on rising crude oil costs, although retail prices remain lower than a year ago at this time.

“A rebound in crude oil prices has fueled up gasoline prices in the last week across the United States, with even bigger spikes in the West Coast, where refinery problems have returned,” said Patrick DeHaan, GasBuddy senior petroleum analyst.

The national average stands at a four-month high, although prices remain at their lowest since 2009, and far lower than a year ago.

The national average has increased 8.2 cents per gallon in the last week to $2.54 a gallon, according to gasoline price website

Late last week, West Texas Intermediate crude oil stood near $58 a barrel, the highest since Dec. 15. That price is $10 a barrel higher than a month ago, and has been a key contributor to the rise in gasoline prices that many states are witnessing. Refinery issues along the West Coast have added insult to injury for Californians, where prices are up 25 cents per gallon just in the last week in some areas, DeHaan noted.