It isn't only OPEC that is making big money off the energy crunch and its soaring gasoline prices.

Big oil companies are making nearly 11 cents a gallon more on gasoline than they were a year ago, and service station operators in the Washington area and nationally are making 6 1/2 cents more.

These increases, along with the well-publicized 29-cent-a-gallon increase going to oil-producing countries and companies, add up to the whopping 47-cent-a-gallon average increase that motorists have paid during the past year.

These figures are based on an analysis of statistics provided by the U.S. Department of Energy and other sources. They include some guesswork because some oil company statistics are secret and the Energy Department information is not entirely up to date.

The average price of a gallon of gasoline in Washington now is about $1.17, up from 70 cents in January 1979.

That's a 67 percent increase. The oil companies increased their take 56 percent, the dealers 100 percent and the producers 94 percent during the 13-month period.

While the tax increase was only 5 percent nationally during the period, a top Energy Department insider who asked not to be identified predicted the federal government will slap a big new tax on gasoline when the election is over and that the states will soon be in a race to put on new taxes of their own.

The legislatures in Maryland and Virginia are considering such increases but so far there has been no action.

These statistics may not hold true for individual oil companies and service stations. They complain that the costs of doing business have soared, and some may be losing money.

But the statistics underline that big money is being made off the energy crunch, and not just by OPEC, the Organization of Petroleum Exporting Countries.

In the most recent local example of this, a bitter squabble erupted last week before a committee of the Maryland legislature in Annapolis as the big oil companies and the local service station dealers fought over who's going to get the lion's share of new revenues generated by soaring gasoline prices.

Exxon's eastern region sales manager, John Adkins, charged that the "average" Exxon dealer in Maryland has doubled his income since 1978, and that therefore there is no need to pass a service station rent control bill that is being proposed to the legislature by the dealers.

Indeed, according to the representatives of big oil companies who testified, the companies need the income from increased rents because their traditional profit centers -- exploration and production -- are no longer as profitable.

The oil companies hardly ever raised rents to their dealers in past decades because their main objective was to have many dealerships through which to build big market shares and unload their vast quantities of profitable petroleum products.

Now supplies are tight and the new profit centers of the industry are refining and marketing -- thus the big new 11-cent increase in "refiner margin" and the push by the big oil companies to raise dealer rents.

The dealer struck back in Annapolis by charging through their spokesman, Vic Rashed of the Greater Washington-Maryland Service Station Association, that big oil is "making money hand over fist."

"When they increase rentals to dealers, what they're really doing is circumventing federal price controls," Rasheed said. "The person eventually picking up the tab is the consumer."

The bill under consideration would tie dealer rent increases to the rise in the Consumer Price Index and would decrease rents when oil companies slash supplies to dealers as they are doing now.

Under federal price controls the oil companies may pass on to dealers and the public only their increased costs for raw materials and other capital and operating expenses.

Under the same controls dealers may pass along only the cost of the gasoline plus an add-on "dealer margin" of up to 16.1 cents a gallon for their other expenses and for their profit. What the dealers charge for repair work and automobile accessories is not controlled.

Exxon's Adkins said the average Exxon dealer in Maryland had a margin of 7.8 cents a gallon 13 months ago and of 16.1 cents -- the maximum -- today, a 106 percent increase.

"We're not yelling about the dealers making a lot of money," an Exxon spokesman said. "That's fine, but don't allow somebody to plead to the legislature that he's going broke when that's not the case."

Replies Rasheed: "The refiner margin has now outstripped the dealer margin, something that's never happened before. The dealer is making his margin on 40,000 gallons but the refiner is doing it on four zillion gallons . . ."

Several dealers testified at last week's hearing, including Exxon dealer August F. DeLuca of Adelphi, Md. DeLuca had been in his spot at 2301 E. University Blvd. for 16 years, paying a rent of $800 a month. Three years ago the rent started going up -- to $1,397 and then to $1,825 a month.

Exxon, which owns the property, says it is worth that much rent based on its appraised value. "The rent has been increased, insurance goes up, everything is up," said DeLuca.

But he is making more money now. Although Exxon has cut his supply, he usually gets enough from the state's special "setaside" supply each month to make up for that.

Without checking his books in detail, DeLuca agrees he may be making about $8,000 a month from gasoline sales now instead of the $4,000 a month he was making before the gasoline crunch began last spring.

"The situation is a little better than it's been, but it seems like just because we're doing a little better, they raise the rent," DeLuca said.

Laurel Texaco dealer John McMullan, on the other hand, is clearing several hundred dollars a month less from gasoline sales than he was before the energy crunch because he had relatively high margins and low volume to begin with, he said.

Now that volume has been cut further by Texaco's supply cutbacks and the state setaside hasn't made up all the difference.

"Shoot, if we had a 100 percent increase I could retire," McMullan said. "We're down maybe $500 or $600 a month with our expenses up."

An Exxon spokesman in Houston said that a comparison of last-quarter figures for 1978 and 1979 showed that "our costs have gone up even faster than we've pushed through price increases, so we're losing money."

Most of Exxon's most dramatic gasoline price increases, however, are not contained in those figures -- 8 cents a gallon this January and an additional 3 cents a gallon Saturday.

Since mid-December, the company has raised its prices 17 cents a gallon -- a 25 percent wholesale price increase in just six weeks.