Rationale

Following a subcommittee members participation in a technical review meeting of ISO Grease testing specifications, several improvement suggestions for D1264 were made at the December 2025 subcommittee meeting. These elements currently appear in the ISO 11009 water washout test method and it was agreed that incorporation would improve the ASTM test method without impacting test operation or precision. The first change is to harmonize the reporting section with ISO 11009. Including requiring a description of the test grease and water following the completion of the test. This information may provide useful information for how the grease and water are interacting beyond the % weight loss from water washout that is the primary result output of the method. Other changes are expansions to procedural notes currently in the method to address known issues with fully drying test greases following the test run. A change to Note 5 giving users direction on how to run an optional blank test to quantify the impact of evaporation loss on the final test result. This is for users information only and is not accounted for in final test result. The second is a revision to Note 6 that allows operators with history on specific products that typically require higher drying temperatures, or samples that have been tested to show minimal impact of oil evaporation on test results to proceed directly to elevated drying temperatures to assure the sample is fully dried in a single drying period.