Many motors have 'lifetime lubrication' although that doesn't guarantee they'll never have bad bearings.
Some motors have cups where you're supposed to drop in oil.
For equipment that is outdoors, check and/or apply its lubrication once a year. The hot and cold cycles tend to bring out a problem, if one is developing.
Use grease in places where oil would be thrown off from moving parts, or would drain off, or would evaporate in high temperatures.
Use oil to get at places where grease cannot be applied.
Some parts (example, rubber seals, automotive wheel bearings) need a special type of grease.
Some parts (example, rubber, plastic) should not get petroleum products on them.