This method covers the laboratory determination@ using a glass hydrometer@ of the density@ specific gravity@ or API gravity of crudepetroieum@ pc;troleum products@ or mixtures of petroleum' and.nonpetroleum products no~mally handled as liquids@ and having a Reid vapor pressure (ASTM Method D 323@ Test for Vapor Pressure of?? Petroleum Products (Reid Method)2 or IP 69) of 26 Ib or less. Values are. measured on a hydrometer at convenient temperatures@ readings of density being reduced to 15 C@ and readings of specific gravity and API gravity to 60 F@ by means of international standard tables. By means of these same tables@ values determined in anyone of the three systems of measurement are convertible to equivalent values in either of the other two so that measurements may be made in the units of local convenience. The hydrometer method is most suitable for determining the density@ specific gravity@ or API gravity of mobile transparent liquids. It can also be used for viscous oils by allowing sufficient time for the hydrometer to reach equilibrium@ or for opaque oils by employing a suitable meniscus correction. When used in connection with bulk oil measurements@ volume correction errors are minimized by observing the hydrometer reading at a temperature close to that of the bulk oil temperature.