The U.S. trade deficit dropped slightly in November to $1.66 billion, the Commerce Department reported yesterday. A fall in oil imports to their lowest level for 4 1/2 years helped to shrink the trade gap from October's $1.86 billion.

The nation's trade account was $29.49 billion in the red in the first 11 months of this year, the department reported, compared with a deficit of $33.22 billion for the same period last year.

A strong balance of payments is one of the bright spots of the economy at the moment and has helped keep the dollar high on the foreign exchange markets. This year's total deficit on trade will be considerably less than last year's $37.3 billion red-ink figure, a Commerce spokesman said yesterday.

Oil imports dropped sharply in volume terms last month, while oil prices remained relatively stable, the report showed. The United States imported 172.1 million barrels of oil and related products during November, a decline of 7.6 percent from October's level. The volume of oil imports was the lowest for one month since May 1976. The value of oil imports totaled $5.74 billion last month, 6.8 percent down from October's level.

Falling demand for imported cars was another important factor in the nation's improving trade performance last month. The value of imported cars, excluding those from Canada, fell by $160 million in November to $1.1 billion. This drop followed an even bigger fall of $210 million in October.

The Commerce spokesman said the fall over the two months was "pretty significant." Imported, as well as domestic, cars have been hit by a falling off of demand for autos, contrary to the hopes of auto manufacturers that the market would revive with the new models this fall. Present record-high interest rates have contributed to the weakening of auto sales.

With a surplus on invisible trade of goods and services -- such as tourism -- and profits and dividends on overseas investment, the United States now is running a surplus on the overall current account of the balance of payments. It is one of the few oil-importing industrial nations to be in surplus.

The improvement is partly due to earlier decreases in the value of the dollar, which have made U.S. goods more competitive, and partly to the recession this year, which dampened domestic demand and so reduced imports.

Last month's trade gap was the third-smallest so far this year. The September trade deficit totaled $1.64 billion.

Exports and imports dropped last month, after rising in October. The 2.4 percent drop in U.S. exports in November left them running at a seasonally adjusted annual rate of $18.6 billion. Exports had risen by 2.1 percent in October.

U.S. imports fell by 3.1 percent last month to a seasonally adjusted annual rate of $20.3 billion, the Commerce report said. This just outweighed a 3 percent rise in imports in the previous month.

The fall in oil imports helped to cut the nation's deficit with oil exporters from $2.66 billion in October to $2.44 billion last month. The deficit with Japan shrank to $953 million from $974 million in October, while the U.S. surplus with Western Europe also dropped from $1.35 billion in October to $1.14 billion last month.