As part of his campaign to sell a windfall profits tax on oil, President Carter exclaimed that the oil companies "are already awash with their greatest profits since the OPEC embargo."

Sen. Thomas Eagleton (D-Mo.), one of several bitter opponents of the other part of Carter's plan, decontrol of crude oil prices, cosiders oil company profit levels "obscene."

What motorists in Los Angeles waiting in line to buy gasoline think about oil company profits probably can't be printed, what with prices up 10 cents to 15 cents a gallon so far this year and still not enough to go around.

The companies still are reaping the legacy of the use of the great political power they held for so many years. Control of the world oil market has slipped from their grasp and into the hands of OPEC (the Organization of Petroleum Exporting Countries), but the public's perceptions do not reflect the oil industry's new role.

Moreover, a shortage of gasoline is threatening American's deep emotional tie to their automobiles, an intrustion into their sense of personal privilege so serious that it demands a villain to pillory.

It should come as no surprise, then, that suspicious consumers blame the companies for the unexpected scarcity and soaring prices; and that they suspect that these are tied to emormous profits for the oil companies.

But are Carter and Eagleton and all the other critics right? Are the companies awash with profits? Are their earnings "obscene?"

A close look at the finances of 27 large oil companies for the last decade shows decisively that the industry's earnings are not spectacular - even when adjusted for some of the industry's peculiar accounting practices and relatively low federal income tax burdens. Certainly the earnings are far less spectacular than the political diatribes they inspire.

Nevertheless, almost all of the 27 companies - each of which had sales of $1 billion or more last year - are doing significantly better these days thanimmeniately prior to the quadrupling of oil prices. Decidedly, higher prices for oil have not hurt the big companies, with one or two exceptions.

And some small companies and individual operators - aided by preferential treatment in the oil price control regulations mandated by the same Congress now so upset by profits of the large companies - have done extraordinarily well. Large private fortunes still are being made in oil.

But the big companies, everyone's favorite whipping boys, have not been major beneficiaries of the huge increase in oil prices since 1973, the analysis shows.

By far the majority, of all those extra dollars being extracted from irate motorists by the spinning dials on gasoline pumps are going to the oil-exporting nations, whether members of OPEC or not. The oil companies are garnering only a small portion of the monopoly profits the OPEC cartel is generating.

Naturally, the oil industry itself defends its profits as reasonable and not very different from the earnings of other industries. And oil executives all maintain that their business should not be subject to any special taxes.

"The industry is becoming the victim of big numbers," complains Theodore Burtis, president of Sun Co. "Our operations are on an immense scale, and all the numbers have a lot of zeros behind them."

"If you look at our rate of return, it's not out of line," says Mobil Chairman Rawleigh Warner Jr.

Energy secretary James Schlesinger, with words far different from Carter's, seems to argee. It is "a misconception that at this point oil company profits are spectacularly high," he says. They "certainly are reasonable."

Reasonableness, like obscenity, lies in the eye of the beholder. One good test of reasonableness, however, comes from a variety of comparisons between the large oil companies and non-oil industrial companies of similar size.

When sales are used to indicate randing, 10 of the 20 largest industrial corporations in the country last year were oil companies - though they long have been doing many things besides finding and pumping oil out of the ground.

Blostered by the biggest of all, General Motors Corp., and its $3.5 billion in profits, the non-oil 10 earned $12.2 billion in 1978, even though one, Chrysler Corp., had a loss. The 10 largest oil companies, on the other hand, made a total of $10.2 billion.

GM's profit was more than $700 million higher than that of Exxon - by far the largest oil company - even though Exxon had $41.5 billion worth of assets compared to GM's $30.6 billion.

More importantly, the non-oil corporations did better in terms of the basic measure most financial analysts and economists would use to compare profits at different companies: the aftertax rate of return on stockholder's equity.

The persons holding a corporation's common stock are its owners, of course. Their equity, or ownership interest, is essentially the difference between the value of all of the corporation's assets and all of what it owes. The rate of return is current earnings divided by the amount of that equity. Similarly, when a savings and loan association pays 5 1/4 percent on passbook savings accounts, that is the rate of return on a saver's investment.

Using this key measure, the non-oil corporations among the top 20 industrials earned an average 14.5 percent return in 1978. The oil 10 earned less, 12.9 percent.

Strikingly, the top seven corporations in terms of rate of return were not oil companies, though numbers 8, 9 and 10 were.

The rate of return within the oil group ranged from a low of 9.0 percent for Texaco - which last year made only slightly more than it did in 1972 even though its sales have more that tripled - to 15.1 percent for Standard Oil Co.(Indiana).

The spread was much greater among the non-oil Big 10. This is not surprising because several industries are involved. There the return on stockholders' equity ran from IBM's 23.1 percent down to Chryler's loss.

If the oil company profits are "exorbitant," "outrageous," "undeserved" or "unearned," as members of the House and Senate have described them, why are there no complaints about the massive earnings of GM, or of General Electric, or Procter & gamble, or Du Pont? (IBM, of course, was sued 10 years ago by the Justice Department for alleged antitrust violations and the suit still is being tried.)

Of all the 27 oil companies that had sales of $1 billion of more last year, the top rate of return on equity, 22.1 percent, was earned by Standard Oil (Ohio), whose Alaskan crude finally began to flow. Coca-Cola, Boeing and 3-M Corp. did almost as well. Lockheed, Avon Products, Keoolgg, Levi Strauss, NCR and the Washington Post, among others, did better.

More comprehensive comparisons, such as one offered recently by Emil Sunley, deputy assistant Treasury secretary for tax policy, in testimony to the Senate Finance Committee, also indicate that oil companies are not doing much better than non-oil manufacturing companies.

Using data from Standard & Poor's "Compustat" file covering 3,000 publicly held corporations, Sunley found that in 1977 the after-tax rate of return on equity was slightly less, 14.7 percent, for companies engaged in oil and gas extraction than for non-oil manufacturing corporations, whose return averaged 14.8 percent. The larger integrated oil companies - those with refining and marketing activities as well as oil and gas production, which includes all of the 27 mentioned above - had a still smaller return, 13.5 percent.

Big oil did do much better in 1974 immediately after oil prices rose to sharply, partly on the basis of large gains on the sale of inventories that had been accumulated at much lower cost. That year, the integrated oil companies averaged an 18.4 percent return on equity compared with 13.0 percent for the non-oil companies. By 1976, however, the integrated companies again had slipped behind the other group.

Oil industry critics, however, argue that oil company accounting methods cannot be trusted. One of them, James Flrg, director of the Washington-based Energy Action group, asked at Mobil Oil's annual meeting in Kansas City two weeks ago that the company open its books to outsiders, calling for "an end to the lying about supplies and costs and profits."

The industry's accounting, like that for all companies, is marvelously elastic. All the same, oil companies have some special opportunities to make their balance sheets look better of worse in the short run. Most of them relate to how a company treats the expenses incurred in looking for oil and gas.

Almost all of the major companies treat the cost of preliminary geophysical surveys as a current expense. And when a well is drilled, they also consider all "intangible drilling costs" - anything, such as wages, that doesn't relate to a piece of equipment - as current expense.

In most industries, such expenses would have to be capitalized, that is, counted as a capital investment that would be recovered bit by bit during the time the oil well was productive. This process of counting as an expense each year the reduction in value as an asset wears out is called depreciation.

The industry's approach of "expensing" a portion of capital investment inflates current costs and reduces current reported profits. At the same time, it also reduces reported levels of capital investment.

One tricky question that different companies handle in different ways is what to do when the hole in the ground turns out to be dry. There have been major disagreements among accountants on this point, and the Securities and Exchange Commission, unhappy about both alternatives now in use, has a committee at work trying to come up with a more realistic approach.

The larger companies generally use what is called the "successful efforts" approach. That simply menas that when they come up with a dry hole, they write it off right away as a current expense, which further reduces current reported profits.

The smaller companies, of which there are at least 10,000 in the industry, argue that the dry holes are all part of the ball game, and that their cost is really just part of the cost of finding producing wells. So they take the "full cost" approach, capitalizing the dry hole expenses along with those of producing wells. This increases current reported earnings, which the small companies say they need to do to keep attracting investors and their money.

One point beyond dispute is that oil company books do not reflect the companies' true worth. All that oil in the ground is worth far more than it used to be. Yet normal accounting practices do not allow the companies to claim a gain of that sort.

The critics point to all these accounting problems and conclude that the industry is not reporting all of what ought to be counted as profits. However, investors in the stock market can count, too, and oil company stocks have not performed as if the industry was sitting on a hidden bonanza.

Fortune magazine has calculated a total return to investors for the major companies in its list of industrials for the last 10 years. It assumes someone bought stock in one of the companies at the end of 1968 and sold it at the end of 1978. In addition, of course, the buyer would have gotten dividends and any stock splits or stock dividends.

Over the decade, investors in the 10 largest oil companies would have received an average annual return of 5.5 percent, according to Furtune. That's better than the non-oil group, with investors in Chryler and ITT losing money, and the return on the others averaging 4.4 percent. (One of Fortune's 10 largest non-oil companies, Western Electric, a wholly owned subsidiary of American Telephone and Telegraph, is not included in the calculation because it is not possible to invest in its stock separately.)

In sum, the oil companies, big and little, and their stockholders are doing very well, thank you. But obscene? Hardly. CAPTION: Table, Big Oil in 1978 By Bob Barkin - The Washington Post; Illustration, no caption.