Cummins Onan RV QG 3600 LP Oil Capacity, Oil Type, and Tips

There are people who do not think that they need to change the oil. They pay a mighty high price when they do not do it very often. Protect your generator’s engine and make sure it stays properly lubed before you have to buy a new one.

Different models will take different types of oil. In the LP generators, the recommendation was SAE 30W but in 2020 the company changed its recommendation to 10W 30 with API "SP" / ILSAC GF-6.

To learn more about the oil capacity. Type of oil to use and more, just continue to read our article. It has the information you want to know about if you own an Onan generator. Take a few minutes to see what these specs are all about.

Cummins Onan RV QG 3600 LP Oil Capacity


The oil capacity for this model of Onan generator is 1.6 quarts. This seems to be the standard size for all Onan generators. There are companies that will sell lubrication kits that come with enough oil to fill this tank.

How you use the leftover oil is up to you. According to the manual, you can use the same oil you use in your vehicle’s engine as long as it meets the proper standards. Those standards are the SG/CE API requirements.

You can exceed those requirements and not harm your generator’s motor. Then the leftover motor oil and be put in your vehicle’s crankcase to help keep it full and lubricate your vehicle’s engine.

Don’t throw the excess oil out unless you are going to take it to the oil reclamation outlets. Putting oil in the trash is a big no-no these days as is dumping it down a drain or into a sewer line.

Onan Propane Generator Oil Type


According to the manual, you should be using Onamax 15W 40. This seems to be Onan’s special label or brand made specifically for their generators. However, you have some freedom in this area.

If you want, you can use different brands of oil that you like better. Some people use Amsoil, Mobile, Shell, and more. As long as the viscosity is the same and it meets those standards mentioned above, then you should be fine.

It is believed that the 15 x 40 is for normal ambient temperatures. Some owners have reported that they have gone down to 10 W 30 for cold weather starts. They have not had a problem doing this but everyone’s experience may be different.

Other owners simply follow the manual as they feel those are the best instructions you can get. Usually, they are. But feel free to change brands if it saves you money.

You may have to stick with the Onan brand oil filter as it is taller and easier to work with. This does not mean it is better but it makes your oil changes easier to do.

There is one fact you should know about, the Onan oil brand is not made by Onan. It is made by another oil company so changing brands is not a problem. You are not using Onan oil anyways.

Onan 3600 LP Generator Oil Change


One of the reasons Onan places a frequent oil change schedule on their generators is due to their location. Most of these generators are located under your vehicle, close to the ground, and in the middle of a lot of blowing dust, dirt & debris.

That location places its generators in the severe service condition. After the 20-hour break-in period, Onan says for you to change the oil every 50 hours. That may be a long time for some people and too short for others.

Other people have stated the first oil change comes at 25 hours and the next at 125. But they were doing that from memory and they are most likely making a slight mistake or two.

The best thing to do in this case is to check to see what the manual says and follow those instructions. From what we have seen, these generators are not cheap and it is best to pay a little for oil instead of a lot for a generator.

Onan Generator Maintenance Kit


If you are not sure which oil brand to use, Onan does put together a nice maintenance kit, so you can get the right parts every time. They are on sale in a variety of places and you can get them directly from Onan if you want.

We are doing the price from memory and believe it to be on sale for roughly $70 through the company. Other companies have the cost listed a bit lower at $60 approx.

What is included, and this is baffling, is an air filter, 2 quarts of oil, a spark plug and that is all. Why the oil filter is not there is beyond us. But it is there in other similar kits.

You can buy the kit or you can buy all the parts you need separately. The latter option may be the cheaper way to go at some stores, especially when you use Onan compatible alternatives.

Check around your parts stores to see what you can find and at a price, you can live with.

Some Final Words

When it comes to oil, you have a lot of brand freedom. The brand is not that important even though some lesser-known brands may not have the best oil inside the can.

If you stick with the best brands, then you know you are getting the best quality oil as long as you stick with the standards and the proper viscosity. Then if you do not own this model of Onan Generator, make sure to read our article Oil Type: What Oil Does my Onan Generator Use?

That article will give you some top advice on those other models and help you keep them lasting a long time.

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