Jim the odor, is obviously from the oil, a spill, leaky fuel line, or a downdraft in the furnace flue/vent are all possibilities, if the combustion is not venting fully, you are also in danger of carbon monoxide poison. A professional furnace repair person can identify the problem, and prevent further leaks. Cleaning up any oil already spilled is very difficult and time consuming especially if the floor is porous. Factor the cost of all these remedies, and perhaps moving the vented oil tank outside, you will have your question answered.