The sunset was spectacular from the flower-adorned terrace of the Swedish Embassy. The gowns were designer. And the food was smoked reindeer and fresh raspberries.

But the talk was of gasoline.

There were those, with their sleek black official limousines, for whom the problem was not great. They were several high-ranking U.S. government officials including a couple of Cabinet officers and a dozen or so foreign diplomats. And there were others, such as the wives of several American officials, and some members of Congress who don't rate goovernment cars, who could talk of nothing else.

"I haven't seen any of that free gas on the Hill I read about," Sen. Larry Pressler (R-S.D.) told Rep. Bill Frenzel (R-Minn.), although in Pressler's case there seemed to be no personal hardship. I've been running to work," he said.

Rep. Don Bonker (D-Wash.) and his wife Carolyn said they got up and over to their neighborhood gas line by 6:30 a.m. yesterday where they spent 1 1/2 hours inching the two family cars toward the gas pumps. Later in the day, Bonker said, a representative of Atlantic Richfield Co. came into his office "and I sure let him know about it. He was ill-prepared to explain but I can tell you that the oil companies know the tricks of the trade and Congress won't win. The energy situation is more acute here and it may be by design."

The talk of the gas shortage was all part of the scene as Swedish Ambassador and Countess Wilhelm Wachtmeister gave a "summer reception" for 300 or so friends before closing up their Nebraska Avenue residence for the summer and going home to Sweden.

The turnout indicated that nobody stayed home because of empty gas tanks, although some wives let their husbands know that they had been doing time in the gas lines with the family cars.

"I spent 57 minutes in line and then they didn't fill the tank," said Mrs. G. William Miller, whose husband, chairman of the Federal Reserve Board, seemed impressed that she had timed the wait so precisely.

The wives of Agricultural Secretary Bob Bergland and Interior Secretary Cecil Andrus both filled up the family cars while their husbands were chauffered to and from work in government cars. "For the business day at least," said Andrus, "I don't have any worries."

Andrus said he thinks everybody in the executive branch and in the Congress is looking at all aspects of the energy question and ways of solving it. But while he foresaw no change in the American standard of living, he also predicted that life styles will change. "We are the most wasteful nation on earth and the time has come when we have to recognize that."

Pressler admitted to being irked by the tendency of both the president and the Senate to "slip off into foreign-policy debates" rather than knuckling down on domestic issues like oil and inflations.

"My constituents are up in arms about the energy situation. I go home nearly every week and people out there are desperate for diesel fuel but no one has ever brought up SALT, for instance." Pressler said he will write to President Carter asking that a Camp David summit be called on energy and inflation with leaders of the oil industry, consumer groups and the government. "Oh yes, he'll write me back and say he works very hard on them." CAPTION: Picture, Countess Wilhelm Wachmeister and S. Dillon Ripley; by Harry Naltchayan