Reid vapor pressure (RVP) is a common measure of the volatility of gasoline and other petroleum products.
[3] The test method measures the vapor pressure of gasoline, volatile crude oil, jet fuels, naphtha, and other volatile petroleum products but is not applicable for liquefied petroleum gases.
[4] ASTM D323-15a requires that the sample be chilled to 0 to 1 degrees Celsius and then poured into the apparatus;[5] for any material that solidifies at this temperature, this step cannot be performed.
Thus, oil refineries manipulate the Reid vapor pressure seasonally specifically to maintain gasoline engine reliability.
The Reid vapor pressure (RVP) can differ substantially from the true vapor pressure (TVP) of a liquid mixture, since (1) RVP is the vapor pressure measured at 37.8 °C (100 °F) and the TVP is a function of the temperature; (2) RVP is defined as being measured at a vapor-to-liquid ratio of 4:1, whereas the TVP of mixtures can depend on the actual vapor-to-liquid ratio; (3) RVP will include the pressure associated with the presence of dissolved water and air in the sample (which is excluded by some but not all definitions of TVP); and (4) the RVP method is applied to a sample which has had the opportunity to volatilize somewhat prior to measurement: i.e., the sample container is required to be only 70-80% full of liquid [7](so that whatever volatilizes into the container headspace is lost prior to analysis); the sample then again volatilizes into the headspace of the D323 test chamber before it is heated to 37.8 degrees Celsius.