But if it is a large quantity, and it has been stored in a protected area it would be worth paying to have samples tested.
It is hard to see how an oil sitting in drums would 'go bad'.
If the testing is not obscenely expensive, do as EdStainless suggested and you can breathe easier in the long wrong the next time you end up with a few barrels that expire on 12/2016 and you didn't see it until 06/2017 (if the testing proves it's good).
IF the lube oil is bad, or is used and the equipment fails, how much do yo lose? Total cost of the shutdown, the lost production, the replacement equipment, and the repair/re-installation manpower and support (cranes, tooling, admin, support costs like scaffolding and testing and balancing and startup?
If you use the oil, then replace it earlier than the standard interval: The oil is marked "Use by" 15 months ago, right? So, if the standard interval is a two-year oil lifetime, you have nine months left. If the oil has a six month lifetime, it is now 3x oil-lives old.