Crude oil prices slid Thursday on the New York Mercantile Exchange, dropping close to $87 per barrel, as equity markets dropped. Prices fell under an established range between $88 to $92 per barrel, that has been consistent since mid-July. The European Central Bank said it would leave monetary policy intact, taking the rug out from under traders who had bet an economic stimulus package was on the way. West Texas Intermediate crude oil prices with September delivery contracts dropped from Thursdays close near $89 per barrel to $87.28 per barrel. Reformulated blendstock gasoline added 2.88 cents to $2.863 per gallon. Home heating oil gained 0.13 cent to $2.8436 per gallon. Natural gas was at $2.92 per million British thermal units. At the pump, the national average price of unleaded gasoline rose to $3.534 per gallon from Wednesday\'s $3.521, AAA said.