
130 Refining Used Lubricating Oils
the order of 140,000 to 150,000 Btu/US gallon (39,022–41,809 kJ/L), which is com-
parable to the heat content of the heavier fuel oils (Table 5.1).
For most applications, such as fuels used in engines or furnaces, the net heat of com-
bustion is the appropriate measure of energy. This value is sometimes called the lower
heating value, net heating value, net caloric value, or specic energy and assumes
that water produced from combustion goes “up the stack” as water vapor. The gross
heat of combustion, also called the higher heating value, requires that water vapor be
condensed back to liquid water to recover t ...