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ASTM D3525 -Gasoline Fuel Dilution in Used Gasoline Engine Oils by Wide-Bore Capillary Gas Chromatography

Significance and Use

5.1 Some fuel dilution of the engine oil may take place during normal operation. However, excessive fuel dilution is of concern in terms of possible performance problems. This method provides a means to determine the magnitude of the fuel dilution, providing the user with the ability to predict performance problems and to take appropriate action.


1.1 This test method describes a gas chromatographic technique for determining the amount of gasoline fuel dilution in used lubricating oils arising from their use in gasoline engines.

1.2 This test method is limited to gas chromatographs accommodating wide-bore (0.53 mm) capillary columns and that are equipped with flame ionization detectors (FIDs) and temperature programmable ovens.

1.3 There is no limitation regarding the fuel dilution con-centration range that can be determined by this method, however the precision statements apply only to the concentration range of 0.5 % to 20.3 % gasoline. A reporting limit of 0.5 % gasoline fuel dilution has also been included in the method.

1.4 Lubricating fluids recovered from engine crankcases have undergone changes due to heating, volatilization, sheering, oxidation and other reactions, and, as a result, the chromatographic profiles of the gasoline diluents and engine oils often differ significantly from their original patterns. Caution is accordingly advised when comparing quantitative determinations made using new verses used or in-service materials.

Extracted, with permission, from ASTM D3525-20 -Gasoline Fuel Dilution in Used Gasoline Engine Oils by Wide-Bore Capillary Gas Chromatography, copyright ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428. A copy of the complete standard may be purchased from ASTM International,