Fuel Oil and Combustion Values

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

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

Combustion or heating values for some common fuels oil grades:

GradeHeating Value
(Btu/US gal)
Fuel Oil No. 1 132900 - 137000 Small Space Heaters
Fuel Oil No. 2 137000 - 141800 Residential Heating
Fuel Oil No. 4 143100 - 148100 Industrial Burners
Fuel Oil No. 5 (Light) 146800 - 150000 Preheating in General Required
Fuel Oil No.5 (Heavy) 149400 - 152000 Heating Required
Fuel Oil No. 6 151300 - 155900 Bunker C
  • 1 Btu/US gal = 278.7 J/liter

Fuel oil 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.

Great care must be taken with heavier grades of fuel used in oil burners to ensure that the oil is supplied with the proper atomizing temperature. If the temperature is too low the 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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