Reid vapor pressures (RVPs) are sometimes specified by crude oil purchasers, particularly if the crude is to be transported by tanker or truck prior to reaching a processing plant. Purchasers specify low RVPs so that they will not be paying for light components in the liquid, which will be lost due to weathering.
RVP is used to characterize the volatility of gasolines and crude oils. The RVP of a mixture is determined experimentally according to a procedure standardized by the American Society for Testing Materials at 100 °F (37.8 °C). A sample is placed in a container such that the ratio of the vapor volume to the liquid volume is 4 to 1. The absolute pressure at 100 °F (37.8 °C) in the container is the RVP for the mixture.