Prices at the wholesale level plunged 1.6 percent in February, the steepest monthly decline on record, as cheaper oil prices pulled energy costs back down to the levels of 1979 and 1980, the Labor Department reported yesterday.

The cost of home heating oil and gasoline, measured by the Producer Price Index, fell by record amounts last month. A worldwide food surplus also helped push down prices.

The record decline in the overall index for goods at the last stage of production followed a 0.7 percent fall in January. It was the largest decline since the government began keeping such records in 1947.

During the last 12 months, wholesale prices fell 0.1 percent. However, if prices continued to fall during the rest of the year at the rate of the last two months, they would plunge 17.1 percent in 1986. No one expects this to happen.

The sharp declines in wholesale prices since the start of the year should begin to show up at the consumer level within the next few months. Several economists cautioned yesterday that consumer prices may decline only slightly as many "middlemen" and retailers refuse to reduce prices as they try to improve their profits.

Deflation at the wholesale level "is going to go on for several more months," said David Berson, economist for Wharton Econometrics. "Not only are energy prices going to remain low, but agricultural prices are likely to continue at their low levels for the next few months as well." Berson said he expected the decline in producer-level inflation to begin a having major impact on consumer inflation around the middle of the year.

White House spokesman Larry Speakes said that "this decline in prices at the wholesale level will send a strong message to the overall economy: Consumer prices are coming down, and the fears of inflation have all but abated."

"With interest rates falling and inflation clearly under control, expectations for a strong second quarter are high," Speakes said. "We expect to see every segment of American society enjoying this fourth year of the Reagan economic recovery."

Economists generally expect wholesale-level prices to continue to drop during March and April and have reduced their inflation forecasts for the year by as much as 1 percent, to about 2.5 percent for consumer prices and to less than 1 percent for prices at the wholesale level.

Meanwhile, another government indicator showed that production at the nation's factories, utilities and mines declined 0.6 percent, following a 0.1 percent increase in January, suggesting that the economy is still not as strong as the Reagan administration and some private economists have suggested. The weakness of the economy, however, helps to keep down prices and wage costs.

Several economists said yesterday that inflation is expected to remain low because of the lower oil prices, moderate wage increases, and ample supplies of food, which will keep food costs low. The lower inflation picture, and particularly the sharp drop in oil, was the leading factor for the drop in long-term interest rates in the last month to their lowest levels in eight years. The drop in interest rates is expected to increase economic growth and consequently, many economists have increased their forecasts for growth in output this year.

The index for finished energy goods dropped 9.4 percent in February, following a 4.2 percent decline in January. Home heating oil prices dropped a record 26.2 percent and the cost of wholesale gasoline fell a record 11.1 percent, the Labor Department said.

Consumer food prices fell 1.6 percent following a 0.4 percent decline in January, largely due to declines in prices of beef, veal, pork, fresh vegetables and eggs. The index for finished consumer goods, excluding foods and energy, was virtually unchanged for the second consecutive month.

The index for capital equipment rose 0.1 percent in February, offsetting a 0.1 percent decline in January.

In a separate report, the Commerce Department said manufacturing and trade inventories rose 0.7 percent in January, the largest increase since August 1984. Inventories for retailers rose 2.9 percent; wholesaler inventories increased 1.4 percent.

In another report, the Federal Reserve Board said that production at the nation's factories, mines and utilities declined 0.6 percent. For the past 12 months industrial production edged up only 1.6 percent.

Production fell 0.6 percent at factories and 3 percent at mines, but rose 1.4 percent at utilities, the Fed reported.