President Reagan said yesterday that he sees nothing wrong with deputy chief of staff Michael K. Deaver and some associates using diplomatic passports to buy nine BMW luxury cars at a discount, calling it "a standard practice that's been used for many, many years."

But BMW spokesman Thomas O. McGurn said that the German automaker approves only 75 such discounts each year, mainly to career diplomats and international agency employes, and that "very, very few" have gone to administration officials.

The sports car saga shifted into higher gear yesterday as administration sources disclosed that some members of the presidential advance team that accompanied Deaver on a recent trip to West Germany have planned to resell their BMWs at a profit of several thousand dollars.

McGurn said the company considers such factors as an official's prominence in deciding, case by case, which of the nation's 62,000 diplomatic passport holders are eligible for the reduced rate.

Asked whether the company would have offered the 25 percent discount if told that the officials planned to resell the cars, McGurn said: "I'm in the car business, I'm not in the morality business. It's human nature . . . It's an individual judgment."

"There are people asking for discounts all the time," he said. "We're not brokering cars to anyone with a diplomatic passport. It's sort of a PR gesture by the company. We like to have opinion leaders driving our cars."

A White House official said that the car that Deaver bought while arranging Reagan's visit to West Germany would cost $20,000 to $25,000 in this country, and that Deaver will save several thousand dollars, depending on the exchange rate when the car is delivered to the United States. The official said Deaver was not involved with the BMW purchases by other members of the 30-person advance team.

White House counsel Fred F. Fielding is looking into the BMW affair, and other federal offices were checking their parking lots yesterday. A Secret Service spokesman said that no agents had purchased BMWs on the West German trip. A spokesman for Vice President Bush said no members of his staff had purchased cars on Bush's trip to Geneva last spring.

Diplomatic passports are issued to presidential aides, Cabinet secretaries, Supreme Court justices, foreign service officers and some military personnel for official business. Those carrying them generally receive VIP treatment at airports, but must pay a 2.6 percent Customs Service duty when importing an automobile.

A State Department spokesman said the discount Deaver received is considered "a sales promotion device, not a gift." But another department official said reselling a car purchased with such a discount "is really a misuse of the diplomatic passport. It would be frowned on if we did that."

McGurn said his company is upset about "gray market" dealers who import up to 7,000 BMWs a year that must be converted to meet U.S. emission and fuel-economy standards. But he said company dealers provide a discount -- smaller than the diplomatic discount -- to about 2,500 tourists a year who visit Munich and arrange shipment for U.S.-approved cars.

For those granted the "diplomatic price," BMW knocks another 8 percent off the sticker price. By the time shipping and customs duties are added to the cost of the car, officials drive away with an 18 percent net savings