Chemical Differences
As chemical substances, kerosene and No. 2 fuel oil have different maximum distillation temperatures: 400 degrees Fahrenheit for kerosene and 640 degrees Fahrenheit for No. 2 fuel oil. They also have different "flash points," or temperatures at which it's possible for the substances to ignite when mixed with air: the lowest is 100 degrees Fahrenheit for kerosene and 126 degrees Fahrenheit for No. 2 fuel oil.
ASTM Standards
ASTM International, which publishes industrial standards for worldwide use, classifies kerosene and fuel oil No. 2 as distinct materials. Kerosene must meet the ASTM D3699 standard, while No. 2 fuel oil is defined by ASTM D396.
Different Uses
For more than a century, kerosene has been used as a light source when burned in small lamps. It is also used domestically in cook stoves and space heaters. No. 2 fuel oil is also used in domestic settings, but typically burned to heat interior spaces, hence the common name "heating oil." Sometimes No. 2 fuel oil is burned to heat smaller commercial spaces as well.