16 Refining Used Lubricating Oils
the viscosity of petroleum lubricants between 70°F and 210°F (21°C and 99°C).
Viscosity is measured in the Saybolt universal second (SUS), which is the time
in seconds required for 50 mL of oil to empty out of a Saybolt viscometer cup
through a calibrated tube orice at a given temperature (ASTM D2161, ASTM
2012).
The specic gravity of oil depends on the rening method and the types of addi-
tives present, such as lead, which give the lubricating oil the ability to resist extreme
mating surface pressure and cold temperatures. The color of the lubricating oil indi-
cates the uniformity of a particular grade or brand. The oil’s ash and re points
vary with the crude oil’s origin. The ash point is the temperatu ...