Retail pump pricing in the U.S. continued to drop this week, according to data tracked by the Energy Information Agency (EIA), with prices falling in all regions of the country except the West Coast. Gasoline prices also stayed on a downward slope as well this week, the agency said, rising only in the Rocky Mountain region of the country.

According to the EIA’s numbers, diesel dropped an average 1.6 cents this week to a U.S. average of $3.977 per gallon – which is 17.1 cents lower compared to the same week in 2012.

Diesel only increased by a tenth of a penny along the West Coast to $4.117 per gallon, the agency said, with diesel now exceeding the $4 per gallon mark in five U.S. regions: the aforementioned West Coast, California ($4.196), the East Coast ($4.009), New England ($4.135) and Central Atlantic ($4.062).

Retail pump prices for gasoline declined an average of 3.7 cents to a U.S. average of $3.608 per gallon this week, EIA reported, which is 33.1 cents per gallon cheaper than the same week in 2012. Gasoline prices only increased in the Rocky Mountain region this week, rising 2.6 cents to $3.523 per gallon, the agency added.