Depending on the grade it should be reusable as base oil in engines again. Especially those times it was never run between changes.

An early engine like that might use too high a viscosity and perhaps not a detergent based oil. Or raise it to the boiling point of water to expell any accumulated moisture. If there are no basic additives it should be reusable in the same crankcase. Depends what the oil used for that application is exactly.