ASTM D287

ASTM D287 is a standard test method published by ASTM International for determining the API gravity of crude petroleum and petroleum products using a hydrometer.

It measures:

•    API gravity — a petroleum-industry scale that expresses how heavy or light a liquid is compared to water
•    Higher API = lighter oil
•    Lower API = heavier oil

How the test works

•    A hydrometer calibrated in API degrees is floated in the sample
•    The reading is taken at a specified temperature
•    The result is corrected to a reference temperature (commonly 60 °F / 15.6 °C)

The method is used in crude oil testing, fuel and refinery products,  quality control, pricing, and classification in oil & gas.

How it compares to  ASTM D1298

•    ASTM D287 → reports API gravity only
•    ASTM D1298 → reports density, specific gravity, or API gravity
•    D287 is more API-focused, D1298 is more general-purpose

ASTM D287 is best for clear, low-viscosity liquids and less suitable for opaque, waxy, or very viscous samples.