I purchased a home in October 2008 that had a power vented oil furnace. We have noticed now that the windows are starting to be opened in the back of the house that when the vent starts up we get an oil smell that comes in the house. Is this normal or do I need a furnace tune up or is there some other issue? I can't imagine the previous owners ( who built and lived in the house for 11 years) would have tolerated this.....