In this chapter, we discuss several tests for the analysis of liquid fuels and lubricants. The analytical methods described are for base oils, formulated lubricants, and selected biofuels. Tests for formulated lubricants are further divided into new and used lubricants and those for specific types of lubricants (e.g., transmission fluids). The complete list of ASTM methods discussed in this chapter is given in Table 1. Many of the tests described in this chapter are used by manufacturers to ensure the quality of new base oils, components, or finished lubricants. Other tests may be applied to simulate the performance of finished lubricants in actual use. In either case, the ASTM methods allow manufacturers and end users to compare products under carefully defined conditions.