The fuel shortages of the late 1960's and early'70's sparked new interest in recycling used motor oil. Resourceful mechanics and handymen designed their own versions of "waste oil" and "drip oil" heaters, but the dangers and risks they create eliminate them from this article.
Some fleet services were dumping the used engine oil back into the fuel tanks of diesel rigs. If the ratio of engine oil to diesel fuel was low, it would not cause any major problems other than more black smoke from the exhaust than normal. Too much of the heavier oil could rob the engine of power from slower flame travel at ignition. Most fleet mechanics stopped once fuel became readily available again.
A few people saw an opportunity to burn the used engine oil in their furnaces, but they soon discovered that the heavier oil also burned hotter: hot enough to burn a hole in the firebox and beyond into the heat exchanger. An expensive lesson, but it prompted the development of better refractory that could handle the intense heat.
Service stations and repair garages that generate most of today's waste oil put more than engine oil in the disposal tank. Transmission fluid, gear oil, power steering fluid, grease, dirt, and the occasional dose of anti-freeze and water all end up in the "soup".
Before this "blend" can be pressurized and atomized through a burner nozzle, certain actions must be taken.
Allowing the mixture to sit in a tank will settle most of the solids out and the water to go to the bottom of the tank.
The use of a floating pick-up supplies the burner with the cleanest fuel in the tank.
Pre-heating and filtering the fuel is a must, and some systems are designed to do both at once. By wrapping the oil filter with a heating blanket, the burner pump will draw clean oil that flows easier.
If the furnace is suspended or stacked over the oil tank, a pump mounted at the tank helps feed the filter and puts less strain on the burner pump.
All waste oil furnace manufacturers offer complete packages that include a tank designed with upright supports to provide a platform upon which to mount the furnace. With the addition of a chimney and electric power to run the booster pump and furnace, setting up is fast and simple. Ductwork can be used to distribute the heated air more evenly throughout the space, but in a open structure, it is not critical.
Initial installation expenses will certainly be higher than with a furnace that burns #2 fuel oil, but at current fuel prices compared to free waste oil, it doesn't take long to justify the added cost.