Shouldn't a cold Northern Hemisphere winter give oil demand, struggling to recover from recessionary doldrums, a huge lift? Maybe not.Yes, heating oil users have been burning more of the fuel than they would have in warmer weather. But the effect on total demand is muted.The International Energy Agency's Oil Market Report for February points out that heating oil consumption patterns are changing in the developed nations of the Organization for Economic Cooperation and Development (OECD)."The share of oil for heating and power generation in the OECD has been shrinking uninterruptedly over the past decade," IEA explains. "Other energy sources, notably natural gas, renewables,...