burning oil on 2001 Ford Excursion

what are some possible causes of excessive oil consumption?

Asked by for the 2001 Ford Excursion
Oil can be leaked out through a leaking gasket or seal, and sometimes a porous casting cause a leak. Internally in the engine valve seals and guides can suck oil into the combustion chamber. Piston rings/cylinders can wear and let oil pass into the combustion chamber. These are the most common causes of excessive oil consumption.