The benchmark diesel price used as the basis for most fuel surcharges is back below $5 per gallon. 

According to the Energy Information Administration of the Department of Energy, the average retail diesel price in the U.S. last week was $4.964 per gallon, a decline of 6.9 cents from the prior week. It marked the 13th decline in the past 14 weeks. 

The benchmark's first move to less than $5 occurred during three consecutive weeks in August. But then a huge upward move of more than 20 cents on Aug. 29 took the price back above $5. Three weeks later, it's below that mark again.

With the latest decline, the DOE/EIA diesel price is down 84.6 cents since its all-time high of $5.81 a gallon recorded June 20.

Retail prices' upward and downward moves are far smoother and steadier than the jolts that can be recorded in the diesel futures market on the CME commodity exchange. That has never been more evident than during just the past few days.

After price movement during the week of Labor Day showed some of the least volatility it has recorded in recent months, price movement swung into high gear last week, all of it on the way down.

Four days of significant declines in the price of ultra low sulfur diesel (ULSD) on CME last week shed 43.06 cents a gallon off the Sept. 12 settlement of $3.6031 a gallon, with the market falling to $3.1725 per gallon by Friday. There were several statistical points in the market last week, as well as news developments, that appeared to lead to a sell-off, including a significant increase in U.S. diesel inventories reported in the weekly EIA statistical report.