McDonald's isn't saying how many burgers it expects to sell this Olympic year. The company keeps a lid on that kind of information. Similarly, it does not want its competitors to know just how much it is spending to promote itself. But the spending clearly has been heavy this year. The company is one of the broadcast sponsors of the Olympics. Together with its chain owners, the company sponsored the United States diving and synchronized swimming teams. They also sponsor the U.S. Gymnastics Federation and U.S. Swimming Inc., the governing body for the American swimmers. With the help of its licensees, the company built the McDonald's swim stadium on the campus of the University of Southern California in Los Angeles. The facility has been used in some Olympic events.

McDonald's already ranks in the top 20 advertisers in the country. Excluding newspapers and spot radio advertising, the company spent $190.8 million in 1983, according to Leading National Advertisers. It is estimated that it cost McDonald's more than $300 million in all last year to maintain its dominance over Burger King and Wendy's.

For the Olympics, McDonald's came up with television advertising that features ordinary people in street clothes participating in Olympic events and winning. The ads are not as clever as Wendy's popular ''Where's the beef?'' campaign, but the medal campaign is packing them in nonetheless.

''We may be giving away more product, but that means more customers for McDonald's,'' said Mr. Rubner. The promotion extends through the end of August.

This is the second time that McDonald's has used the Olympic medal promotion. The campaign was developed by the Chicago marketers Frankel & Company in 1976 for the Montreal Games. It was so successful, company officials said, they decided to repeat it.