Yes it does. Apart from becoming saturated with contamination so that the contaminants fall out of suspension an form sludge and thicker oil, combined heat and shear forces will cause the viscosity to break down so that it becomes as thin as water and the film thickness that protects surfaces by keeping them apart and frictionless totally loses its effectiveness. Which happens first depends on the engine and type of use to which it is put.
@Cowabunga quick question just for PigIron, if I was to put E7 into a Perkins 4,236, an engine designed to run on SUTO, how often would I need to change the oil
With SUTO oil the oil change interval would be 250hrs of an electric clock
Im thinking I could leave it there for nearly 500hrs