Onan Generator Oil Change

By on Sunday, February 28, 2010

One of the cool things about owning an RV is having the ability to generate your own A/C power when you need it. So today I performed an oil change on my Onan MicroQuiet 4000 generator to keep it running in tip-top shape. The generator manual recommends changing the oil each year. Changing the oil is pretty straight forward and takes less than an hour. There is no oil filter on my model so that's one less thing to worry about. Some generator models do have an oil filter, so review the generator manual for your model before taking on this project.

Before starting I made sure I have the following things on-hand:
  1. 2 quarts of SAE 30 motor oil. The generator takes 1.6 quarts. Oil recommendations vary depending upon the temperature ranges in your area. So be sure to check your manual.
  2. Drain pan and funnel.
  3. T-30 Torx socket for the Torx screws on the drain plug panel (got mine at Sears)
  4. 9/16 socket for the drain plug.
  5. Plumbers pipe thread sealant for sealing up the drain plug before you put it back in.
Changing the oil
The following procedure is pretty simple and outlined in your manual as well:

  1. Run the generator for a few minutes to warm it up before you drain the oil.
  2. Shut down the generator.
  3. Remove the green panel on the underside of the generator that covers the drain plug (see photo). Use the T-30 Torx bit/socket to remove those screws. You only need to remove one screw then loosen the other. You can then just swing the panel off to the side.
  4. Using the 9/16 socket, remove the drain plug.
  5. Drain the oil into your oil pan until all of the oil is drained.
  6. Apply some pipe thread sealant to the drain plug and screw it back in. Use a torque wrench if you have one to ensure you don't over tighten it. Check your manual for the recommended torque.
  7. Remove the oil cover and add 1.6 quarts of new oil. Check your level to make sure you don't over fill.
That's it, you're done! Run the generator for a few minutes and check for leaks before screwing the drain plug panel back on.

Other things to check
Before I button up the generator, I take a few minutes to inspect the air filter, and wipe down visible areas. Finally, I log the date and generator hours in my RV maintenance log.

Performing regular oil changes is important to keeping your generator running efficiently for many years. I also run the generator for an hour each month with the A/C and water heater on. This keeps the generator components lubricated and makes starting easier.

Now let's go do some worry free boondocking!

Need more info?
(Update 9/11/2011)
Many of you have questions that I don't necessarily have answers to, so I've added some links here that may help:


  1. Very informative and timely as I just changed the oil today, 03/13/10. I had to look about 10 minutes to find this site, VERY GOOD!!!!!!!!!!!!!!!!!!

  2. Thanks Jim for the kind words. It's often trial and error for me in these situations. I'm glad you found this post helpful.

  3. Thanks for your informative info, I'm going to put it to work right now.

  4. Thanks Tito....I am just entering the world of RVing and need to watch the budget, this helps!


  5. Just bought an RV. It had no manuals. The generator needed an oil change. At the dealer it was 3 weeks out to get it done. Thanks now I don't have to wait. This was really helpful.

  6. Does this 4000 generator have a oil filter.

  7. The 4000 model in my RV does not have an oil filter. If you have a different model then double check your manual.

  8. Thanks just got trailer did not have manuel, have looked everywhere for that filter.

  9. Thanks for your post, have had a oil leak since coach was new. Suspect the oil plug itself,will try the thread sealant.


  11. Are you sure that's not the air filter on the left hand side?

  12. I was very curious as to what size of Torx socket I needed. I googled it and low and behold your site popped up!Thanks for the information,now if I can only figure out how to axcess the darn spark plug up front and the fuel filter CLEAR IN THE BACK......

  13. What about the fuel filter? Have you changed that? Pics & advice on locating & removing would be very helpful if you have the experience with this.

  14. How often are you supossed to replace the fuel filter on thiS generators. Thanks Javier

  15. Hello Tito,
    Have you changed the spark plug yet? Where is it and the fuel filter.

  16. Did not had owners Manual- you saves me BIG Time!!!! Thx!

  17. what would be the recommended oil for 95--100 degree weather???

  18. pretty cool site Tito
    Thank You

  19. I've only used SAE-30 oil in my Onan which should be adequate for that temperature range. According to Onan "Power output will decrease 1% for each 10ºF increase in ambient temperature above 85ºF. For example, if the outside temperature increases from 85ºF to 100ºF, your air conditioner may require 20-25% more power to run efficiently." Power will also degrade as you climb in altitude, and there is a generator adjustment for that.

    There are other oil options though. I know folks using synthetics or other grades. I use Mobile 1 in my home generator (non an Onan).

    I've added a some links to the bottom of this post that may help answer those questions. Click on the link to the "Onan RV Generator Handbook" and go to page 26-27. There is a discussion on oil types and operating temperature that may be helpful.

  20. Hi,
    What about the fuel filter? Have you changed that?Plz tel me.............

  21. Great tips, I think we should always check our oil supply regularly so that we won't have any problems in the future.
    fuel trailers

  22. Great site! Thanks for all the info.

  23. Do I need to pull the generator unit to check the oil pressure switch? My unit only runs with the start switch depressed.

    1. Sorry. I don't know the answer to that one. I haven't done that.

  24. For all of you interested in this post, I just updated a video I made of my last generator oil change. I hope it's helpful. Enjoy!

  25. Very informative blog & all the steps are very clearly understandable.Oil changing is very important to protect the engine.Thanks for the post.

  26. I’m not that much of a online reader to be honest but your sites really nice, keep it
    up! I'll go ahead and bookmark your website to come back later on. Many thanks

    My web-site get backlinks


Let me know what you're thinking. I welcome your comments. Thanks -Tito

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