ECONOMY

Sales of U.S.-made cars during the first 10 days of August plummeted 20.7 percent from year-ago levels, automakers said. During the period, Chrysler's car sales plummeted 38.6 percent, sales of GM's domestically made cars dropped 22.2 percent and Ford posted a 21.3 percent decline in car sales.

COMPANIES

Sun Microsystems, the leading U.S. supplier of computer workstations, said it has received a letter from Texas Instruments alleging that a ''substantial'' number of Sun's products infringe on TI patents. Sun also disclosed that a tentative agreement reached with IBM to resolve an earlier patent dispute calls for the two companies to enter into a five-year cross-licensing agreement. Both disclosures were made in a registration statement filed with the SEC.

Chrysler Chairman Lee Iacocca confirmed that the firm had talked with Renault, Volvo and Fiat but said he didn't expect a full merger to take place. There has been speculation that Fiat would buy a stake in Chrysler, but Iacocca said no such arrangement is imminent.

Wheeling-Pittsburgh Steel reached a tentative labor accord with negotiators for 5,500 union employees and agreed to a settle claims stemming from eight-year-old wage concessions. The union had planned to strike tomorrow if an agreement had not been reached.

Jiffy Lube proposed a 1-for-10 reverse stock split that it hopes will increase the value of its shares and strengthen the struggling company financially. Shareholders will vote on the proposal at the company's annual meeting Sept. 6.

ACQUISITIONS

MCI and Telecom-USA completed their merger, combining the nation's second- and fourth-largest long-distance telecommunications companies. MCI bought Telecom-USA's outstanding shares for about $1.25 billion, financing the purchase with bank debt and cash on hand.

REGULATION

Eastern Air Lines was granted temporary relief from major provisions in its labor contract with pilots. "It is clear that prompt cost reductions, including pilot labor cost reductions, are essential if an imminent liquidation of the estate is to be avoided,'' Judge Burton Lifland said.

A U.S. trade commission ruled that there is reason to believe that Chinese sparkler imports threaten to damage the domestic industry, triggering a Commerce Department inquiry. The department's findings could lead to import duties.

EARNINGS

Eastern Air Lines reported a net loss of $35.6 million for the quarter ended June 30, compared with a $129.3 million loss in the 1989 period.

Cineplex Odeon said its first-half losses totaled $50.4 million, increasing from a loss of $28.0 million in the year-earlier period. Its second-quarter loss narrowed to $38.4 million from $38.7 million a year ago.

J.C. Penney said six-month earnings rose 4 percent, while second-quarter earnings were down 18 percent from a year ago.

Tele-Communications, the cable TV and theater giant, said it lost $101 million in the first six months, compared with a loss of $115 million a year earlier. It lost $44 million in the three months ended June 30 compared with a loss of $64 million a year earlier.

Live Entertainment, whose businesses include the Waxie Maxie music chain in the Washington area, reported that second-quarter earnings rose 37 percent.

Tiffany & Co. said six-month earnings rose 28 percent while second-quarter earnings increased 27 percent.

PEOPLE

Fed Chairman Alan Greenspan said the central bank lacks the tools to deal surgically with regional economic problems, and that its ability to stabilize the economy on a national level could be hampered if it lost sight of that fact. Greenspan's remarks were in response to questioning by Senate Banking Committee Chairman Donald Riegle (D-Mich.), who asked if problems in New England and the real estate industry could spread and become a national recession, which could in turn interfere with the Fed's monetary policy.

Office of Thrift Supervision Director Timothy Ryan, meanwhile, said in response to questioning by Riegle that he doesn't expect the thrift situation in New England to become as serious as it was in the Southwest.

Charles H. Keating Jr., the former owner of Lincoln S&L, caught up on late mortgage payments to avert foreclosure on his million-dollar suburban Phoenix home.