Light, sweet crude for March delivery fell $1.61 cents to $39.56 a barrel on the New York Mercantile Exchange.
The Labor Department reported 598,000 jobs were lost in January. The unemployment rate rose to 7.6 percent, the highest since 1992.
Oil traders see layoffs as an instant drag on oil demand. People have less need for gasoline when they no longer have a daily commute. They also cut their spending for toys, nonstick pans, raincoats and millions of other products that are made with petroleum.
"The economy's ugly. We know it's ugly," analyst and trader Stephen Schork said. For a sustained rebound in oil prices, "you have to stop seeing the economy contract. You have to stop seeing people get laid off. We probably won't see much of that this year."
The number of people remaining on the unemployment compensation rolls increased slightly to nearly 4.8 million, the most since records began in 1967.
Amid the gloom, some companies are performing above analysts' beaten-down expectations. Wal-Mart's sales beat Wall Street's forecasts and Macy's department store, which this week said it would slash 7,000 jobs, raised its fourth-quarter and full-year forecasts.
Investors are also watching for possible further production cuts by the Organization of Petroleum Exporting Countries, which has already promised to reduce output by 4.2 million barrels since September.