Crude oil prices shifted lower in New York Friday, dropping under $91 per barrel after the White House announced a 60-million-barrel market intervention. The United States and 27 nations of the International Energy Agency said they would draw down their reserves over the next 30 days to offset a loss of roughly 1.5 million barrels a day on the market due to political chaos in Libya. August delivery West Texas Intermediate crude oil in New York hit an overnight low of $90.52 per barrel, but climbed to $90.90, still off $1 from Thursday night. Home heating oil prices on the New York Mercantile Exchange added 1.36 cents to $2.813 per gallon. Reformulated blendstock gasoline prices lost 1.39 cents to $2.7625 per gallon. Henry Hub natural gas prices added 2.3 cents to $4.216 per million British thermal units. At the pump, the national average price of unleaded gasoline dropped to $3.601 per gallon from Thursday's $3.612, AAA said.