is the presence of a continuous lubricating film sufficient to completely separate two surfaces, as distinct from boundary lubrication. Full-fluid-film lubrication is normally hydrodynamic lubrication, whereby the oil adheres to the moving part and is drawn into the area between the sliding surfaces, where it forms a pressure, or hydrodynamic, wedge. See ZN/P curve. A less common form of full-fluid-lubrication is hydrostatic lubrication, wherein the oil is supplied to the bearing area under sufficient external pressure to separate the sliding surfaces.

Most instrument ball bearing applications introduce a lubricating fluid to the contacts with the ideal goal of achieving complete surface asperity separation.  Developed and refined "elastrohydrodynamic lubrication" (EHD) as a practical concept in understanding fluid film lubrication in a working ball bearing. Insights gained from this development include:

• Significant separating fluid films are practically achievable in rotating "point-contact" bearings 

• Such films can support the high contact stresses inherent in ball bearings 

• Contact surface relative velocity, elastically formed footprint geometry, and fluid viscosity are prime determinants of EHD film thickness 

Practical application of EHD theory involves the choice of Lubricating fluid properties (for example: viscosity at operating temperatures) and bearing internal design features consistent with the achievement of nearly complete asperity separation. This requires Film thickness in the order of four or more times greater than the average surface finish values of the ball and

Also see: Boundary Lubrication and Mixed Film Lubrication.