Mercury 858081K03 is a genuine OEM Storage Seal fogging oil for winterization and long-term storage of gasoline engines. Mercury describes it as a 12 oz spray can with a heavy, sticky formula that forms a protective barrier on internal metal surfaces to help prevent rust during storage.

Key Features

• Genuine Mercury Marine / Quicksilver OEM product
• Part number 858081K03
• 12 oz spray can
• Heavy, sticky spray lubricant for internal engine protection
• Helps keep cylinders lubricated to reduce risk of cylinder or piston damage at restart after storage.

Engine Compatibility
Mercury states this fogging oil is suitable for 2-stroke and 4-stroke gasoline engines, including carbureted, fuel-injected, and catalyzed engines. It is marketed for marine use on outboards and sterndrives, while also being usable on other gasoline engine equipment.

Serial Number Fitment Notice
This is a maintenance chemical rather than a model-specific hard part, so serial-number confirmation is generally less critical than it is for mechanical components. Even so, it is best to follow the storage procedure in the engine owner’s manual for the exact Mercury or MerCruiser application being serviced.

When This Part Needs Replacement
Use this product during winterization or before long-term storage to protect internal engine surfaces from corrosion while the engine sits idle. Mercury specifically positions it for off-season storage use.

Installation Notes
Mercury instructs users to follow the engine owner’s manual for use. Retail usage guidance commonly involves spraying the product into the air intake to fog the engine, then protecting cylinders before storage, but the correct procedure should always match the engine’s official service guidance.

Alternate / Superseded Part Numbers

• 92-858081K03
  Mercury also sells a closely related Quicksilver-branded version under 858081Q03, but for this listing the correct Mercury OEM number is 858081K03.

Parts Desk Insight
Fogging oil is one of those small seasonal items that can make a big difference on engines that sit for months. Its main job is not lubrication in normal operation, but corrosion protection during storage, especially on internal metal surfaces that would otherwise be exposed to moisture and air.

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