While Washington area motorists continue to sit in long gasoline lines, many of the multimillon-gallon gasoline storage tanks operated by oil companies here are so full that new shipments are being turned away, industry sources said yesterday.

After being refused here, the gasoline is being sent north to Philadephia and New Jersey in one of two major petroleum piplines that bring 90 percent of this area's gasoline from Gulf Coast refineries, the sources said.

spokemen for the major oil companies say the federal allocation system prevents them from distributing the additional gasoline in the storage tanks to local service stations.

At the same time, interviews with oil company representatives produced a variety of conflicting explanations for the situation. Several expressed the belief that the current surplus would ne temporary.

Government officials trying to grapple with the gasoline situation appeared bewildered by the apparent surplus.

W. L. Nicoll, manager of community relations for Colonial Pipeline Co., which runs the largest petroleum pipline through this area, confirmed that one major tank farm, in Fairfax City, is so full that gasoline is being sent elsewhere.

Nicoll said the oil companies "send it to other destinations because [they] say their inventories are full at Fairfax. They can't take the product because they don't have the [storage capacity]."

Nicoll said that he was not sure why this was happening and that it might be a "temporary situation, a matter of scheduling."

A spokeman for A m o c o said its Fairfax tanks are three-quarters full - fuller than normal.

"We've got a little bit better inventory in our gasoline tanks the last few weeks," said Joseph Golueke, Amoco's distribution manager for the Baltimore region. "The situation is better this year than last in that we don't have any terminal runouts."

A spokesman for Crown Central Petroleum said his company's tanks at another farm at Newington are two thirds full - also fuller than normal. The spokeman said there had been three recent pipeline deliveries during a four-day period and that normally the deliveries are spaced 10 days apart.

As an example of what can happen when a shipment comes in on the pipeline and there is no room for it, one source said that Cities Service was due to receive a 50,000-barrel shipment of gasoline on May 30 and 31 but did not have room for it in the company's Fairfax tanks.

As a result, the small feeder pipeline that comes to Fairfax from the main Colonial pipeline had to be closed for 24 hours until Cities could fird space for the gasoline. During this period, the small pipeline acted as a temporary storage tank for the 50,000 barrels, but no other gasoline could move through the line. A Cities Service spokesman had no comment on the incident.

The spokeman would not say whether the company's Fairfax tanks were fuller than normal. But he said the product flowing through its system there was up 22 percent over last year. He acknowledged that this might tend to make tank levels higher at Fairfax, even though he said the company's overall national gasoline inventories are lower than last year.

A Exxon spokesman said that levels of some gasoline products at Newington are "fairly high, but in perspective this is not surprising."

The perspective, according to the spokesman, is that these big storage tanks in Washington are just a tiny part of the nationwide and regional storage facilities and pipelines run by the big oil companies.

In this view, one tank farm "doesn't amount to a hill of beans," the spokesman for Exxon said. He said tank farms in Washington could be full to overflowing but this would just be a quirk. Spokesmen for Shell, Gulf, Texaco and Mobil denied that levels in their tanks here are higher than normal.

Rep. Joseph l. Fisher (D-Va.), who has been active in seeking to end the gasoline lines here, called the full storage tanks and refusals of new supplies "a puzzle."

"I wounder . . . whether to any extent it's a deliberate policy," Fisher said.

"Something smells to high heaven here," said James Flug, director of Energy Action, an organization that is critical of the oil companies.

"There may be some elements of actually hiding stuff in some form by the oil companies or by intermediaries or agents on behalf of the companies," Flug said. "What is needed now is a real detective job to see where the oil is, how much there is and who it really belongs to The Department of Energy has no idea."

Rep. Herbert E. Harris Ii (D.Va), who has led the effort of local politicians to investigate the causes of the long gasoline lines here, said he has asked the Energy Department for a specific audit of bulk tank levels and refusals of shipments at the two storage sites serving the Washington area.

"I haven't got anything back [from the Energy Department] yet." Harris said. "Ihave got rumors that there is adequate supply in those [tank] farms that is not going out to the [service] stations."

One observer at the tank farms said, "It's common knowledge that the tank levels are higher than normal out here. There's bitterness and resentment among the [oil company] employes here because they stand in [gasoline] lines like everyone else."

Another source with first-hand knowledge said that several weeks ago the oil companies were anxious to get all the gasoline they could for their Washington area bulk tanks, and that this had been the normal state of affairs for years.

"Now they're worrying about what the hell they're going to do with it when it gets here," this source said.

According to these sources supplies of regular and premium gasoline are higher than normal while supplies of unleaded are normal or somewhat below normal.

"Even so, the no-lead is here, it's not being distributed, it could be distributed, there is plenty of it," one observer said.

The Newington and Fairfax City bulk storage facilities consist of pipeline terminal points where the petroleum products - all grades of gasoline heating oil, jet fuel and diesel - are tapped off the pipelines and diverted to nearly banks.

Exxon, Shell andCrown have tanks clustered around the Newington terminal point of the Plantation Pipeline - the last point in that pipeline on its juourney from refineries in Baton Rouge, La.

Gulf, Texaco, Cities Service and Amocco have tanks at Fairfax City at a tap point of Colonial Pipeline there. These companies tap off what they need at Fairfax from the continuously flowing pipeline, which goes on north to New Jersey.

Mobil has a tank farm in Manassas which also taps from Colonial Pipeline.

Mobil recently had to "downgrade" 10,000 barrels of unleaded premium because its tank at Manassas for this product was too full to take more.downgrading meant that the gasoline was put into a tank for regular unleaded, a lower cost product with lower octane, according to a Mobil spokeman.

The incident "had nothing to do with our total gallonage" at Manassas, the spokesman said. He said that total gallonage was somewhat lower than it was last year.

Each company has from 3 to 10 or more of the bulk tanks in this area, each of which holds from 30,000 to 200,000 barrels of a petroleum product. A barrel is 42 gallons.

Delivery trucks, carrying about 8,000 gallons apiece, fan out form the Newington and Fairfax City farms making deliveries to the roughly 1,500 service stations in the Washington area.

Because the constant flow of the pipelines must be in balance with the rate at which the delivery trucks are taking products to customers, the levels in the big tanks rise and fall constantly as the companies perform a continuing juggling act.

Since batches of fuel must be scheduled for the movement on the pipeline up to 30 days in advance, the juggling act can get trickly and tanks can easily be fuller than a company might wish at a given time, oil company spokemen said.

"So while this may appear to be a situation where we have more supply than we need, it is not that," said William R. Snyder, Crown's vice president of administration.

"It's just a case that we're getting our supplies back in balance as a result of a foulup in the scheduling of pipeline shipments."