How to Change Generator Oil? (Portable & RV Generators)

changing generator oil

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Oil lubricates the internal moving parts of a generator engine helping it perform better and live longer. With use, the oil breaks down which increases wear on the moving parts of the engine, until it seizes.

This makes regular oil changes one of the top items in the preventive generator maintenance checklist. Generator oil changes may sound intimidating at first but it is a simple task once you know what to do.

So, how to change generator oil?

First, locate the oil drain plug of your specific generator. Unscrew the drain plug and let the oil drain out on a drain tray. Replace the drain plug once done. Next, locate the oil cap on the engine and unscrew it. Using a funnel, pour in the right type and quantity of oil into your generator’s engine and replace the oil cap.

Changing generator oil doesn’t cost much, but ignoring it can turn into an expensive repair. Worst, you may have to buy a new generator because the engine is beyond repair.

In this post, we’ll take an in-depth look at changing generator oil, especially portable and onboard RV generators. We’ll also talk about the frequency of oil change, type of generator oil, and proper way to dispose of spent oil.

How Often Should I Change the Oil in my Generator?

Changing generator oil on every scheduled maintenance is a good practice. Manufacturers of onboard RV generator Onan recommends changing the oil after 150-200 hours of use. Most portable generator manufacturers recommend changing the oil every 100-150 hours of use.

However, some factors can affect this number significantly. Here is a detailed article about how often should you change the oil in a generator.

What Tools are Required to Change Generator Oil?

A generator’s oil change is a simple task once you have the right tools in place. These tools will make the process more efficient while reducing the time it takes to change the oil.

Here is a list of things you need to have.

  1. Oil type recommended by the manufacturer
  2. A can or tray to collect the drained oil
  3. A new oil filter specific to your generator’s model
  4. Protective hand gloves and goggles
  5. An oil funnel
  6. A right size socket wrench, ratchet, and oil filter wrench
  7. T-30 Torx bit/socket

How to Change the Oil in a Portable Generator?

The most common type of generator used in RVs is portable generators because they are lightweight and versatile. Moreover, portable generator oil changes are very simple.

Here is how to do it correctly.

01. Heat the Generator Engine

First off you need to run your generator for a few minutes to warm up the existing oil inside the engine. By nature, oil increases in viscosity as it cools down. This will slow down the draining process, and your engine will have more oil sticking to its inside.

This is especially true during the winter months, with the drop in temperature thickening the oil. As the engine runs, the heat from the engine returns the oil to its normal consistency making it easy to drain.

Make sure not to run the unit for too long, as draining oil from a hot engine increases the chances of burns. Running the unit for 5-minutes should do the trick.

02. Place the Generator on a Level Surface

Now place your portable generator on a level surface. This will make sure all the spent oil is drained properly and indicate the right level of oil while pouring the new oil in.

Because the ground clearance of a portable generator is very little, you need to place it on a raised platform that is slightly higher than the drain tray. To make sure your drain container fits under your portable generator, you need to place it on a platform.

You can use two similar size blocks or place the generator on a table. However, make sure the unit sits properly, and there is no chance of the generator tipping over.

03. Draining the Old Oil

Before you start draining the old oil, wear a pair of disposal hand gloves to keep your hands clean and glasses to keep your eyes safe.

Now you need to locate the drain plug/nut on your generator. Though the size of the drain nut varies depending on the generator’s model and brand but is generally a ⅜” nut.

You can refer to the user’s manual of your model to find out the exact location and size of the drain plug. However, in most models, it is on either side, underneath the engine.

Once you find the drain plug, place a drain try underneath the drain hole to collect the spent oil. You can use a drain pan like the Lumax Black LX-1632 or any waste container lying around.

With the right size ratchet, remove the drain plug/nut. The old oil will start draining through the drain hole. Give it some time until all the oil drains out or stops dripping. Opening the oil fill cap on the motor will let air in, speeding up the draining process.

Next, inspect the drain plug and the washer for damage and dirt. Clean if dirty or replace if damaged. Now put the drain plug back from where you removed it and tighten it with a ratchet. Make sure not to overtighten it, or you risk stripping the threads.

Note: Draining spent oil onto the ground will contaminate the soil or other water bodies.

04. Check the Oil Filter

Now is a good time to check the oil filter and replace it if necessary. Locate the oil filter and open it using oil filter pliers like the one from WORKPRO. Replace it with the right type of oil filter as recommended by your manufacturer.

05. Pour New Oil

Before you start pouring in new oil, make sure the drain plug is firmly put back in its place. Pouring new oil into the engine with the drain plug open will drain the new oil out.

For inverter generators, you need to open the service panels on the side to access the oil fill cap. However, there are no service panels for open-frame-type generators.

Now insert a funnel into the oil filling chamber and start pouring the new oil slowly. The type and quantity of oil vary depending on the brand of the generator. Thus make sure you check the user manual to find out the type and volume of oil to be used.

Moreover, the temperature and climate will also affect the type of oil you should use in your generator. Generally, you’ll need a thinner oil during the winters and thicker oil during summer.

Next, remove the funnel and close the oil fill cap once you have filled in the recommended quantity of oil.

06. Check for Leaks

After filling in the oil, run your generator for a few minutes and turn it off. Next, open the oil fill cap and check the dipstick to ensure you have the right amount of oil in it. Lastly, check for leaks or oil dripping through the drain and oil cap.

Here is a video illustration of a portable generator oil change.

How to Change the Oil in an RV Generator?

Unlike portable generators, changing the oil in an RV generator is a little more involved. However, the general idea for both is the same.

This oil change procedure is for Cummins Onan RV generator, a common onboard generator for RVs and travel trailers.

  1. First, park your RV on level ground to drain and fill oil properly
  2. Run the generator for 5-minutes to warm up the oil
  3. Now slide under your RV generator to access the oil drain panel
  4. Using a T-30 Torx bit/socket, remove the green panel that covers the drain cap. You just have to remove one screw on the panel and push it to swing it to the other side
  5. Open the drain plug/nut using the right size socket. Make sure you’re not directly below the drain cap to prevent oil from draining on you
  6. Drain the oil into an oil pan like the Lumax Black LX-1632 or any other container you have
  7. Inspect the drain bolt and the washer for any damage. Secure the drain bolt using a ratchet. Don’t over-tighten the nut, as it will increase the risk of stripping the threads
  8. Check the oil filter and replace it if needed
  9. Next, open the service panel and remove the oil fill cap. Fill in the right type and quantity of oil using a funnel. Make sure not to overfill the oil.

Now, run the generator for a few minutes and check for leaks and then replace the green panel on the drain cap.

Here is a video illustration of an Onan generator oil change.

What Kind of Oil do you Put in a Generator?

The type of oil you put in your generator determines its performance and longevity. You need to use high-quality oil that is recommended by the manufacturer.

You need to use a thinner oil if you will be using the generator in colder climates. A 5W-30 rated oil is the ideal choice for running your generator smoothly in cold weather.

On the other hand, you have to use thicker oil when using your generator during the hot summer months. A 10W-30 or a 15W-40 rated oil works best in warmer climates.

Make sure you refer to the user manual of your specific generator for the type and quantity of oil to be used.

Can I use Synthetic Oil in my Generator?

Though you need to check the manufacturer’s recommendation, using synthetic oil in generators is not an issue. Synthetic motor oil has a chemical composition that protects and lubricates the engine better.

However, make sure not to use a single or multi-grade oil as it may hurt your generator’s engine.

How to Properly Dispose of Motor Oil?

Once you have changed your generator oil, you need to dispose of the old spent oil. However, you can’t just throw the old oil anywhere you like.

Motor oils can be very damaging to the environment. It can contaminate the soil and water bodies. Moreover, you can’t even throw it in your dumpster.

Find the hazardous waste disposal site in your area where they collect and recycle spent/old motor oil. You may also contact your local auto repair shops as many collect old motor oil for various use.

Disposing of old oil in any place other than the mentioned is not permitted by law.