The suggested engine oils that should be used for a Honda XR100 have a rating of 10w-30, which include Pro Honda GN4, HP4 4-stroke Oil, Honda 4-stroke Oil or anything that is equivalent, as stated in the owner's manual. The Honda XR100 is air- and oil-cooled. As a result synthetic engine oils are most suitable since they flow easier in colder environments, exhibit no loss of prime, are highly resistant to viscosity breakdown and possess longer change intervals.
Regular oil inspections and changes are crucial in maintaining the engine's life, and will help remove dirt and debris that have deposited on the surfaces. A Honda XR100 running on insufficient engine oil will be prone to engine and transmission damages.