The price of oil has stabilized over the past week, but is still at its lowest level in years, while fuel prices show no signs of letting up from their dramatic declines.

New U.S. Energy Department figures show the average cost for on-highway diesel is down 13.8 cents over the past week to $3.281 per gallon, its lowest level in four years. This is 59.2 cents less than the same time a year ago and compares to a high for the year of $4.021 in March.

Prices fell over the past week between 4.2 cents in New England for an average of $3.425, also the highest priced part of the country, to as much as 17.9 cents in the Midwest to $3.294. Compared to a year ago prices in the different parts of the country are down between 51.5 cents to as much as 65.5 cents less.

Trucking’s main fuel is the least expensive in the Gulf Coast region at $3.175, down 15.3 cents over the past week.

The result of this big drop has been billions of dollars in savings for the trucking industry, $350 to $375 million dollars annually for each one-cent decline, according to the American Trucking Associations.

Meantime, the cost of crude oil moved lower on Monday, falling $1.87 to $55.26 per barrel, following a rally on Friday that pushed prices 5% higher. Compared to last Tuesday’s opening price it is down just 14 cents.

It’s estimated the more than 50% decline in oil prices in the second half of this year and the consequential fall in gasoline prices has also led to a $125 million windfall for consumers, according to the investment banking firm Goldman Sachs, enough for it to label the drop a “middle class tax cut.”