The average price of a gallon of unleaded gasoline slid 3.2 cents to $2.802 for the week ending July 20, according to federal records.

The incremental changes in national gasoline prices since the middle of May have been punctuated in recent weeks by a sharp spike in California gasoline that's been attributed by the Los Angeles Times to several refineries going off-line.

Gasoline is now 79.1 cents lower than it was a year ago, and declined in price in six regions, while rising in the Rocky Mountain, West Coast and West Coast without California regions tracked by the U.S. Energy Information Administration. The Midwest saw the sharpest decline of 5 cents to $2.671, while the Rocky Mountain region rose 2.3 cents to $2.841.

Among states, California remained the most expensive at $3.875 in AAA's Daily Fuel Gauge Report. Six other states have at least $3-per-gallon gas, including Nevada, Washington, Oregon, and Idaho ($3.049). Six states have gasoline that's cheaper than $2.50 per gallon, including Louisiana ($2.496), Tennessee, Arkansas, Mississippi, Alabama, and South Carolina ($2.373).

Meanwhile, the price of diesel fell 3.2 cents to $2.782. Diesel is now $1.087 lower than a year ago.