When a railroad has a slump in traffic what procedures are followed in storing engines. Are the diesels run every so often? Are fluids drained?
Assuming you mean diesel locomotives, i.e. NOT "engines", EMD has a published procedure for proper storage of units. It is fairly elaborate, such as running the prime mover for so many minutes with a special oil "preservative" in the lube oil, and then draining ALL the fluids from the locomotive.