Facts about the ASTM D5188 Standard Test Method
ASTM D5188 is a Standard Test Method for Vapor-Liquid Ratio Temperature Determination of Fuels (Evacuated Chamber Method). It covers the determination of the temperature at which the vapor formed from a selected volume of volatile petroleum product saturated with air at 0 to 1°C (32 °F to 34 °F) produces a pressure of one atmosphere in an evacuated chamber of fixed volume.
The ASTM D5188 test method is applicable to both gasoline and gasoline-oxygenate blends. (Andreas Schwarzmann, R&D)
The vapor-liquid ratio of the fuel indicates the tendency of a fuel to vaporize in automotive engine fuel systems. Their specifications generally include T (V/L = 20) limits to ensure products of suitable volatility performance. For high ambient temperatures, a fuel with a high value of T(V/L = 20), indicating a fuel with a low tendency to vaporize, is generally specified; conversely for low ambient temperatures, a fuel with a low value of T(V/L = 20) is specified.