There are a lot of products out there that claim to improve engine oil and provide a layer of protection for the engine internals. These additives typically come in the form of a spray or bottle that is added to the engine after an oil change. Depending on the product, these additives may claim to protect the engine from rust and corrosion, reduce wear, help break up sludge and increase fuel efficiency. There is a wide variety of engine oil additives available and it’s easy to get overwhelmed in the oil additive aisle at your local auto parts store.
There is a class of rust preventive oil additives that are used in combination with the base oil to create an ashless and water free lubricant. These rust preventive oils are used in the oil industry for permanent protection of metal surfaces from corrosion during storage and shipping. These rust preventive oils are typically formulated to be compatible with petroleum and synthetic lubricants.
These rust inhibitors are generally non stains, have detergent and dispersant properties and have better performance at lower concentrations. They are also vapor phase corrosion inhibitors and provide the best protection when in direct contact with metal surfaces.
These are usually used in conjunction with VCI (Vapor Corrosion Inhibitors). These additives help protect the lubricant from oxidative deterioration by blocking oxygen molecules in the lubricating oil. Oxygen in the lubricant can cause degradation of the metal surfaces and cause the formation of acids that attack the lubricating oil.