U.S. Stocks Gain as Oil Falls  NEW YORK (Reuters) - U.S. stocks closed higher on Monday  after a drop in oil prices eased worries about high energy  costs, although disappointing earnings from diversified  manufacturer 3M Co.&lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=MMM.N target=/stocks/quickinfo/fullquote"&gt;MMM.N&lt;/A&gt; curbed gains on the blue-chip Dow.