I feel much better double checking this, and thats why I'm making this post. I have a friend who has about 100 gallons of either kerosene or kero/fuel oil blend. He switched heat sources to gas and no longer needs it.. While I heat with wood, I still heat my DHW with the oil furnace. I figure even if it is straight kero, its still safe to burn in the furnace because thats essentially #1 fuel oil. However, this stuff is also 5 years old. Can I just add some diesel fuel conditioner to it, or should I just use it as a solvent instead of a fuel?