"Can I use a lubricant after its expiration date to lubricate a machine? What test is required before its use?"
Whether you should use a lubricant after its expiration date depends on the type of lubricant. For instance, if it is a highly additized lubricant like engine oil, the likelihood of the additives stratifying (separating out of the oil) and settling to the bottom of the container is very high. However, if it is an R&O (rust and oxidation-inhibited) oil with few additives, this would not be as critical of a concern.
In addition, you must consider how the lubricant has been stored. Has it been left out in the elements or was it stored indoors with air conditioning and desiccant breathers on the containers to stop dust and moisture from entering the oil?
Also, how long has the lubricant been stored — two months, five years, etc.? Is the lubricant used in a machine that is critical for production or is it utilized in a component that has a lot of redundancy (backup processes) and will not affect production if it goes down?
The volume of oil is another important factor in whether you should replace the lubricant, throw it out or have it tested and reconditioned. If there is any question as to the quality of your oils, you should have them tested or replaced. Of course, you must determine whether it is cost-effective to have the lubricant tested/re-additized.
After you have answered these essential questions, the following tests should be performed:
It is recommended that lubricant oils be stored no longer than 12 months and greases no more than six months. Also, for optimal protection of your machines, use the first-in/first-out (FIFO) storage method to maintain lubricant freshness.