Foam can seriously compromise the protection qualities of a lubricant.

Lubricant foaming can be caused by a number of factors, including over-or under-filling a component and water, coolant and sealant contamination.  Areas of the country that have recently experienced flooding often have a high level of vehicles experiencing foaming problems.

Foam is made up of air bubbles suspended within the lubricant.  A minimal level of foam is normal, but too much foam compromises the lubricant film necessary to adequately protect components, leading to increased wear and component failure.

Significantly overfilling a component with too much lubricant is one cause of lubricant foaming.  If the engine oil pan is overfilled, parts which are usually out of reach, including the crankshaft, hit the oil and whip it into a foam.  The foam takes up more space than a liquid and begins to work its way out of the component, often through the dipstick tube, PCV system, seals or gaskets in engines and the vent tube in differentials.  Under-filling a component may also put it at risk for lubricant foaming, allowing air to enter the pump and the fluid to become contaminated more rapidly.

Transaxles and differentials often have special instructions related to proper lubricant fill levels.  While it was once common to simply fill differentials until the lubricant was level with the fill hole, it is common to find applications that call for a fill level below the fill hole, emphasizing the importance of knowing the particular requirements for a piece of machinery.

Lubricant contamination may also lead to foaming.  Moisture entering the engine as condensation, a byproduct of combustion or through a coolant leak usually increases foaming problems.  Components which have been submerged in water are at an especially high risk for foaming and should have contaminated fluids changed as soon as possible to avoid component failure.  Assembly sealants are another source of potential lubricant contamination that can cause foaming.

Using a high quality lubricant, maintaining proper fill levels and keeping the lubricant free of contaminants are key to preventing foaming problems in engines, transmissions, transaxles, transfer cases and differentials.  Amsoil Synthetic motor oils and drivetrain lubricants are formulated with premium antifoam additives that effectively keep foam to a minimum, allowing the lubricant to deliver superior protection and performance for extended drain intervals.  In fact, Amsoil Universal Synthetic Marine Gear Lube exhibits outstanding resistance to foaming even when subjected to 10% water contamination, providing superior protection and performance in marine applications.