Particles can bond with each other to form larger solids. Solid particles may clog filters and block oil galleries. Solids may dam up around bearings. Heat must be quickly transferred away from metal surfaces. No industry standard for testing or how much is safe to use in automotive engines.
Lubrication is a complex science.
In addition to these characteristics, the physical aspects of the lubricant such as flash point, boiling point, viscosity index, total acid number, total base number and corrosion tests play crucial roles in determining the ability of the lubricant to withstand the harsh environment in an internal combustion engine. Motor oils must have the ability to lubricate, cool, clean and seal. In order to do this, extensive additives are added to all motor oils by their manufacturers. Moreover, the lubrication requirements for gasoline and diesel engines are quite different. Obviously, these small, hand-operated devices do not even come close to duplicating the mechanical complexities and extreme conditions that exist in an internal combustion engine.