Crude oil slipped under $90 per barrel Monday, with price movement slight and traders cautious two weeks before Election Day in the United States. November delivery of West Texas Intermediate crude oil gave up 55 cents to $89.89 per barrel on the New York Mercantile Exchange. Natural gas prices lost 1.3 cents to $3.604 per million British thermal units. Home heating oil lost 0.96 cents to $3.108 per gallon. Reformulated blendstock gasoline added 0.9 cents to $2.673 per gallon. At the pump, the average price for a gallon of regular unleaded gasoline was $3.665 per gallon, down from Sunday\'s $3.776, AAA reported.