Quick and Easy Onan 4000 Generator Oil Change for Your RV

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Quick and Easy Onan 4000 Generator Oil Change for Your RV

Table of Contents

  1. Introduction
  2. Preparing the Generator
  3. Removing the Oil Cover
  4. Locating the Oil Plug
  5. Draining the Oil
  6. Using an Alternative Oil Collection Method
  7. Cleaning the Area
  8. Reattaching the Drain Bolt
  9. Checking for an Oil Filter (Even Though There Isn't One)
  10. Refilling the Generator with Oil
  11. Final Steps and Tips

Changing the Oil in Your Generator: A Step-by-Step Guide


Changing the oil in your generator is an essential task that ensures its smooth and efficient operation. Regular oil changes help maintain the generator's performance and prolong its lifespan. In this article, we will guide you through the process of changing the oil in your generator, providing step-by-step instructions and valuable tips along the way.

Preparing the Generator

Before starting the oil change process, it's crucial to prepare your generator properly. Begin by locating a flat and stable surface to park the generator. Ensure the generator is positioned in a well-ventilated area to minimize the risk of inhaling fumes. Next, allow the generator to run for a few minutes to warm up the oil, ensuring better drainage.

Removing the Oil Cover

To access the oil plug, you first need to remove the oil cover. The oil cover is typically secured by screws, such as a Torx T30. Carefully unscrew the screws using a ratchet and quarter-inch drive. Set the cover aside, keeping it safe for reattachment later.

Locating the Oil Plug

Once the oil cover is removed, you will be able to locate the oil plug. However, the oil plug is not immediately visible and is hidden behind a cover. Remove the cover by unscrewing the screws holding it in place. Use a 12-millimeter wrench to loosen the oil plug.

Draining the Oil

Prepare yourself for a little mess as you begin draining the oil. Place an oil pan underneath the oil plug to catch the oil. Loosen the oil plug completely and let the oil flow out. The oil plug may have a washer, so ensure it doesn't get lost in the pan. Allow the oil to drain fully until it's reduced to a trickle.

Using an Alternative Oil Collection Method

If you don't have an oil pan handy, you can use a five-quart container with the side cut off as an alternative method for collecting the oil. This makeshift oil collector can be particularly useful if you are on the road and need to replace the oil in your generator. Make sure the container is empty and place it strategically to capture the oil efficiently.

Cleaning the Area

After the oil has finished draining, it's essential to clean the area around the oil plug and the engine. This step helps prevent oil residue from accumulating and ensures a clean workspace. Use a rag or a paper towel to wipe away any oil spills and drips. Cleaning the area thoroughly reduces the risk of oil migration and potential contamination.

Reattaching the Drain Bolt

Once the oil has been fully drained and the area is clean, it's time to reattach the drain bolt. Tighten the drain bolt snugly, ensuring it is secure but not overtightened. Take this opportunity to double-check the washer and ensure it is in place and properly seated. Keeping the washer intact prevents leaks and maintains the oil's integrity.

Checking for an Oil Filter (Even Though There Isn't One)

At this stage, you may wonder about an oil filter and whether your generator requires one. However, contrary to some expectations, most generators, including this model, do not have an oil filter. It's important to know this to avoid wasting time searching for a non-existent oil filter. Focus on the oil replacement process instead.

Refilling the Generator with Oil

Now that the old oil is drained and the drain bolt is securely in place, it's time to refill the generator with fresh oil. Refer to the manual for the recommended oil viscosity and density range for your specific generator model. In this case, we are using Rotella 15W40, which has proven to be a reliable choice for RV generators.

Pour the oil carefully into the engine oil fill cap, using a funnel for precision. Given the limited space, it's advisable to use a smaller funnel that can fit in the tight area without causing spills. Slowly pour the oil, ensuring it doesn't overflow. Follow the manual's specifications for the recommended oil quantity, which, in this case, is 1.6 quarts.

Final Steps and Tips

After filling the generator with the correct amount of oil, replace the engine oil fill cap tightly. Check the oil level using the dipstick to ensure it reaches the appropriate level. Wipe any excess oil off the dipstick and reinstall it securely. At this point, your generator is ready to be used with its fresh supply of oil.

Remember to dispose of the used oil responsibly and in accordance with local regulations. It's advisable to store the used oil in a suitable container and take it to a recycling center or an authorized oil disposal facility. Regularly changing the oil in your generator not only preserves its performance but also contributes to the overall longevity and reliability of the machine.

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