U.S. gasoline costs fell to their lowest level in four months, with the national pump price dropping 1.8 cents over the last week to $1.866 a gallon, the government said Monday.

The average price for regular unleaded gasoline is up 12 cents from a year ago, but the cheapest since May 3, according to the Energy Information Administration's (search) weekly survey of service stations.

Gasoline costs dropped ahead of one of the busiest driving periods of the year — the Labor Day holiday. The decline mirrors a drop in U.S. oil prices, down about $7 a barrel since hitting a ensive regular unleaded gasoline, with the price up 4 cents to $2.06 a gallon. San Francisco topped the agency's city survey of gasoline costs, with the price rising 7.2 cents to $2.129 a gallon.

The Gulf Coast (search) had the cheapest fuel by region, with the price down 2.2 cents at $1.78 per gallon. Houston had the lowest pump price at $1.745 a gallon, down 1.5 cents.

The weekly report also showed gasoline prices were up 3.6 cents to $1.991 in Seattle, down 2 cents to $1.946 in New York City, down 4.9 cents to $1.908 in Chicago, down 1.4 cents to $1.863 in Miami, and down 7.8 cents to $1.783 in Cleveland.

Separately, the EIA survey said the average pump price for diesel fuel decreased a slight 0.3 cent to $1.871 a gallon, up 37 cents from a year earlier.

Truckers on the West Coast paid the most for diesel fuel at $2.051 a gallon, down a penny from the prior week. The lower Atlantic states had the cheapest diesel at $1.815, down 0.3 cent.