When is desiccant replaced for an engine being stored?

• A. 10%
• B. 20%
• C. 30%
• D. 40%

Answer: (D)

When an engine is stored, desiccant packs are used to keep the surrounding air dry and prevent moisture-related corrosion inside the engine. The desiccant works by absorbing moisture, but its capacity isn’t infinite. As it becomes more saturated, its ability to remove additional moisture diminishes. The standard maintenance guideline is to replace the desiccant when it reaches about 40% moisture content. At that point there’s still some remaining capacity, but it’s approaching exhaustion, so replacing it ensures the storage environment stays adequately dry. Replacing earlier would be unnecessary maintenance, while waiting longer could allow moisture to accumulate and increase the risk of corrosion.

If the desiccant uses a color indicator or a weight check, you’d follow the manufacturer’s indication to determine when that 40% point is reached.