Average heating oil prices continue to plummet in Maine, down 42 cents over the past week to $4 a gallon, according to the latest survey by the state's energy office.

The state credited falling national demand for petroleum products, including gasoline, for the price slide.

Average oil prices in Maine ranged from a high of $4.26 a gallon in central Maine to $3.40 in the southwest, the survey found.

The average kerosene price hit $4.58.

In early July, the average oil price had soared to $4.71; kerosene was $5.12, according to the state survey.