Is It Better to Burn #1 or #2 Fuel Oil in a Furnace?

#1 Fuel Oil

• You may recognize this fuel oil by its more common names, coal oil or kerosene. It burns nearly as effectively as #2 fuel oil, producing 135,000 BTUs, or British thermal units, of heat per gallon of oil. Although the name coal oil implies that it is dirty -- which was true only two decades ago -- advances in refinery equipment and technology produce a clean-burning fuel today. This type of fuel oil is not affected by extremely cold temperature, below 0 degrees Fahrenheit, so it is a good choice for homes in mountainous areas or the northernmost regions of the country. In addition, homes with outside oil storage tanks usually burn kerosene, as these tanks are exposed to cold and snow for extended periods.

#2 Fuel Oil

• The common name for #2 fuel oil is home heating oil. It burns cleanly and produces heat at the rate of 138,500 BTUs per gallon. It is difficult for #2 fuel oil to catch fire. The refining process leaves almost no vapor. This kind of fuel does tend to clump up and clog the heating system when the temperature falls below 30 degrees Fahrenheit. This is better fuel oil to burn when the oil tank is inside the house, as it is safer than coal oil. An exception is when your home is in a very cold region and the basement is unheated.

Fuel Oil Blend

• Refineries produce a product known as the winter blend. It consists of at least 80 percent #2 fuel oil, with the remainder #1 fuel oil. This is a good choice for homes with unheated basements where the temperature dips below freezing but never gets as cold as 0 degrees. This blend combines the higher heat output of home heating oil with the nonclumping properties of kerosene.

Increasing Burn Efficiency

• While the BTUs noted represent the heat-producing capacity of both types of fuel oil, your actual level of burn efficiency depends on proper maintenance of the furnace and heating ducts. An important tip is to always refill the oil tank while the gauge is still above 1/4 full. Oil has a small amount of sediment that settles in the bottom of the tank. The amount of this sediment builds up over the years. When the oil tank is nearly empty, suction pulls sediment from the tank and into your furnace. This sediment clogs burner nozzles and air filters, resulting in a cold house in the middle of winter.