U.S. retail sales fell sharply last month, the government said Thursday, as gas prices plummeted and auto sales slowed. The Commerce Department reported that retail sales dropped 0.8 percent in January, following a 0.9 percent decline in December. The dollar value of gas station sales plunged 9.3 percent, the largest drop in six years. Auto dealer sales also fell for the second straight month. Outside those categories, sales ticked up 0.2 percent after a flat reading in December. The slight gain suggests that Americans are still cautious about spending their windfall from lower gas prices, which economists expect will save the typical family $750 this year. Cheaper gas and strong hiring have sent consumer confidence to seven-year highs, a sign that spending should increase soon. Excluding the volatile categories of autos, gas, building materials, and restaurants, sales rose just 0.1 percent after falling 0.3 percent in December. Consumers spent more last month at electronics, building materials, and general merchandise stores. Restaurants and bars saw another month of solid business. Restaurant sales have jumped 11.3 percent in the past year.