If you don't regularly change the oil on your portable generator you run the risk of causing serious damage to the generator. You should change its oil every three or four times that you use it, especially if you are running the generator for long periods of time. The owners manual will have all of the information that you will need to service your portable generator.
Bring the portable generator onto level ground. Make sure that if you were to spill any oil it would not damage grass or any other living thing around you. Place some unfolded newspaper on the ground and set the portable generator on top of the paper.
Place the oil pan under the oil compartment on the portable generator. The oil compartment is labeled "OIL" on top of the cap on top of the engine. Use the ratchet set to remove the drain nut that is at the bottom of the oil container on the engine of the portable generator.
Drain the oil container into the oil pan for five minutes. Replace the drain nut to the bottom of the oil container with the ratchet set.
Remove the oil cap from the top of the engine. Place the funnel into the oil container and pour the new oil into the oil container on the generator. The owner's manual will have the specs for what type of oil is to be used and how much.