This test method covers the determination, using a glass thermohydrometer in conjunction with a series of calculations, of the density, relative density, or API gravity of crude petroleum, petroleum products, or mixtures of petroleum and nonpetroleum products normally handled as liquids and having a Reid vapor pressures of 101.325 kPa (14.696 psi) or less.
The method offers simple measurement and direct temperature measurement. It is faster than the pycnometer method. The advantage over ASTM D1298 is that it not uses a separate thermometer.
Applications are crude oil tank measurements, refinery process control, custody transfer, pipeline quality verification or marine terminal operation.
The method helps ensure that engine oils from different manufacturers can be mixed without causing phase separation or loss of performance.
Precision: The method is based primarily on visual observations of homogeneity and miscibility rather than numerical measurements. Because the results are qualitative (pass/fail), no conventional repeatability and reproducibility statistics are specified. Reliable results depend on strict adherence to the prescribed temperature cycling and observation procedures.
Test: The test oil is blended with a series of standard reference oils and subjected to a controlled cycle of heating and cooling. After conditioning, the samples are visually examined for separation, haze, gel formation, sediment, or other signs of incompatibility. An oil passes the test if it remains homogeneous and fully miscible throughout the procedure.
