WASHINGTON — The U.S. trade deficit narrowed in October to its lowest point of the year after Americans bought fewer foreign cars and imported less oil.

The shrinking trade gap boosted growth over the summer and may do so again in the final three months of the year. But economists worry the trend could reverse next year, especially if Europe’s debt crisis worsens.

The Commerce Department said today that the trade deficit shrank 1.6 percent to $43.5 billion. It was the fourth straight monthly decline.

Overall imports fell 1 percent to $222.6 billion, which largely reflected a 5 percent decline in oil imports. The average price of imported oil fell for the fifth straight month to the lowest level since March. Oil prices rose last winter because of turmoil in the Middle East and North Africa.