FTM 5414 (FED-STD-791 Method 5414) Resistance of Grease to Fuel
Grease used in carburetor controls, valve stem seals and other aircraft and automobile applications may come in contact with hydrocarbon fuels. If the fuel dissolves or deteriorates the grease, the system may no longer be properly lubricated. This test first determines the amount of grease that dissolves in a given amount of solvent and then visually determines changes in the grease in the presence of solvent.
To determine the amount of grease that dissolves in the test fluid: A known quantity of test grease is placed in a centrifuge tube, solvent is added and the tube is shaken until the grease is evenly dispersed in the solvent. The mixture is centrifuged until two layers are completely separated and the upper layer is clear. An aliquot of the clear fluid is removed, the fluid is evaporated, the residue weight is determined. The percent of the sample dissolved in the solvent is reported.
To visually determine deterioration of grease in solvent: a strip of aluminum is coated with the test grease, and half immersed in the solvent for several hours. The strip is removed, dipped in fresh solvent and examined for defects including blistering, cracking and loss of adhesion. It is then dried for 24 hours and re-examined for defects. The results of both visual observations (before and after drying) are reported.