Crude oil futures ended down on Tuesday, dropping from Monday's eight-week high, as the dollar's strength and forecasts that weekly inventory data would show domestic crude stocks rose pressured the market. A sharp drop in RBOB gasoline futures, also from eight-week highs hit on Monday, dragged crude futures lower as well. Gasoline fell after gaining in four of five previous sessions. A stronger dollar usually affects demand for commodities as it raises costs for users of other currencies.