In an article yesterday in the Washington Post on the 9 percent increase in crude oil imports by American oil companies, it was reported that this increase represented 385 million additional barrels of oil. The 9 percent increase actually represented 77 million barrels of additional oil during the first five months of 1979.

While American motorists were waiting in gasoline lines earlier this year, U.S. oil firms were importing 9 percent more crude oil than they did in 1978.

A detailed examination of oil company records show that among those crude oil import increases for the first six months of 1979 were: Gulf Oil Corp., up 23.5 percent; Ashland Oil, up 19.6 percent; Mobile Oil Corp., up 17.9 percent, and Exxon U.S.A., up 15.5 percent.

The import records are filed monthly by each oil company with the Department of Energy (DOE) and are certified by the firms as accurate under penalty of law.

In interviews, executives of Gulf, Exxon and Mobil acknowledged that their imports -- and their total crude supplies -- were up substantially, despite the shutdown of the oilfields in Iran for 10 weeks at the beginning of the year.

None of the company officials offered an explanation of how this summer's gasoline shortage was touched off in the face of fast-growing imports.

"We at Mobil don't make or create gasoline lines, that's an industry phenomenon," said Bonner Templeton, a vice president for supply and distribution.

Said Jon Deakin, senior vice president for Gulf's oil supply arm, "That's always the thing that's hard . . . because I know we maintained our refinery runs pretty consistently this year . . . insofar as we are concerned, our level of crude supply was pretty well sustained."

"Where did the oil go? You've got me bothered by the fact that I don't have a satisfactory answer to the question," said Anthony L. Seaver, manager of the planning division at Exxon International.

It was reported this week that worldwide oil production was up 5.8 percent in the first six months of 1979. And federal energy officials have reported in the past that total U.S. crude imports were up.

However, DOE officials have never presented these figures on a company-by-company basis.

Until now, federal energy officials have explained the summer gasoline shortage in part by saying that refiners used their increased crude supplies to rebuild their reserves, that they used their refineries at less than capacity and that to some extent they cut gasoline production in favor of other and more profitable oil byproducts like jet fuel. At the same time, federal officials have said that gasoline demand rose artifically earlier this year as panicky motorists and other consumers began topping off their tanks.

Total crude oil import figures from company records show that in the first five months of 1979 U.S. oil firms imported 385 million barrels more than in the first five months of last year.

That much crude oil would have supplied an additional three weeks of driving gasoline to American motorists this summer, according to the National Petroleum Refiners Association.

While crude oil imports rose this year by 9 percent, demand for gasoline in the nation rose by approximately 3 percent, according to oil industry spokesmen.

Even as imports increased steadily in the first half of 1979, oil companies cut gasoline supplies to service stations by as much as 15 percent. The resulting tight market led to a 50 percent increase in the price of gasoline.

The records show that just after Iran stopped oil production on Dec. 26, the U.S. companies sharply increased their crude oil imports from other nations including Saudi Arabia, Kuwait, Nigeria, Algeria and Venezuela.

For example, Exxon, the nation's largest oil company, had been importing approximately 3 million barrels of Iranian oil for U.S. use each month before the Iranian shutdown.

Yet, when it lost 9.4 million barrels of Iranian oil in April, May and June, Exxon replaced that amount with imports from other countries and still increased its overall crude imports by 5 million barrels compared with the like three months in 1978.

Indeed, just as Iran concluded its first full month of shutdown in January, Exxon was setting its record for a single month's imports -- 26.6 million barrels.

Executives at Exxon, Mobil and Gulf and federal energy officials offered varying explanations of why gasoline supplies to the public were reduced in the face of rising crude oil supplies.

A spokesman for Exxon declined to provide specific information to show how Exxon's additional crude oil was used this year.

"The numbers you want are simply not going to be made available because they never were made available before," said Margaret Earle.

Another Exxon spokesman said that, generally, Exxon used some of its additional crude to build up reserves, which had been drawn down in the first quarter of 1979 to meet higher demand for gasoline and to replace "marginally lower" supplies of domestic crude oil.

The spokesman, Seaver, of Exxon International, said that while Exxon's crude oil supplies were higher than 1978, they were not as high as the company had planned.

Seaver declined to disclose what the company had projected for its crude oil needs this year.

Peter Wolgast, manager of Exxon International's planning and analysis division, had said in an interview last Friday that "our actual imports were lower [in 1979] than they had been at the same time in 1978."

Yesterday, Wolgast acknowledged that "when I went back and checked, I found the opposite." He said that while crude oil imports were up by about 15 percent, imports of refined fuel oil and gasoline were down by about half as much. Still, he said, the figures had increased overall.

At Mobil, where crude oil imports were up almost 18 percent, Templeton said that his company used some of the additional oil to build up its reserves of gasoline in order to prepare for refinery shutdowns for maintenance this fall.

By July, Templeton said, Mobile had more than a million additional barrels of gasoline in reserve than it normally maintains to prepare for those shutdowns.

"In hindsight, we could have released that million barrels and our inventory wouldn't have gone below last year's level," Templeton said.

He said Mobil was operating this year with about 52,000 additional barrels of imported crude supplies. Part of that, he said, was to make up for a loss of 15,000 barrels a day of domestic crude oil that Mobil could no longer buy, leaving a net increase of 37,000 barrels a day.

Templeton said that during the period of the gasoline shortage Mobil's crude oil reserves remained fairly constant, wtih 21 million barrels in January, 19.5 million barrels in April, and back to 21 million barrels in May.

At Gulf, Deakin acknowledged that crude oil imports were up by 23.5 percent, but added that imports of refined fuel oil and gasoline were down. Gulf increased its net imports of oil and oil products by about 10 percent in the first six months of 1979, Deakin said.

He said he could offer no specific explanation of why there were lines at Gulf stations just as there were at other stations.

"It's always hard comparing statistics," Deakin said. "You're really comparing apples and oranges -- what you planned to import and the marketing environment. One reason we were able to run our refineries so well is because we were not relying on Iranian crude."

Les Goldman, assistant secretary of energy, professed surprise over the 9 percent increase in crude oil imports. Nonetheless, he said consumer demand was larger than the oil supply could accommodate this summer.

On Feb. 7, then secretary James R. Schlesinger told the Senate Energy Committee that the Iran shutdown would reduce oil imports by 500,000 barrels a day.And in a special report to be president released three weeks ago, the DOE said that imports in February through May this year increased by only 3.3 percent over last year.

Goldman defended both of those positions, despite the oil company records showing a 9 percent crude oil import increase.

He said Schlesinger was right, because DOE views the increased import figures as a "reduction" since imports were not as high as they might have been if Iran had not stopped oil production.

Goldman also said that the 3.3 percent figure cited in the report to the president referred to total figures for imports of all petroleum products, including substantial quantities of residual fuel oil used primarily by electric utilities to power generating equipment.