Fuel Oil and Combustion Values

Combustion value in Btu/gal for fuel oils No.1 to No.6

The heating or combustion value of a fuel can be expressed as the quantity of heat (Btu per gallon) released during the combustion process where oxygen from the air reacts with the hydrogen and carbon in the fuel.

The combustion or heating value for some common fuels oil grades are indicated in the table below:

GradeHeating Value
(Btu/US gal)
Fuel Oil No. 1 132,900 - 137,000 Small Space Heaters
Fuel Oil No. 2 137,000 - 141,800 Residential Heating
Fuel Oil No. 4 143,100 - 148,100 Industrial Burners
Fuel Oil No. 5 (Light) 146,800 - 150,000 Preheating in General Required
Fuel Oil No.5 (Heavy) 149,400 - 152,000 Heating Required
Fuel Oil No. 6 151,300 - 155,900 Bunker C
  • 1 Btu/US gal = 278.7 J/liter

No. 1 and No. 2 fuel are both used for residential heating purposes. The No. 2 is slightly more expensive but the fuel gives more heat per gallon used.

The No. 1 fuel oil is used in vaporizing pot-type burners. The No. 2 is used in atomizing gun-type and rotary fuel oil burners.

The heavier the grade of fuel used in an oil burner, the greater the care must be taken to ensure that oil is supplied the combustion process at the proper atomizing temperature. If the temperature is too low the fuel oil will not atomize and evaporate and the burner will not operate efficiently.

Related Topics

  • Combustion - Boiler house topics - fuels like oil, gas, coal, wood - chimneys, safety valves, tanks - combustion efficiency

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