What Kind Of Oil For an Onan 5500 Generator? (Oil Capacity)

Every mechanical device needs lubrication. However, not every oil type or brand out there is designed to work with every mechanical device. When it comes to Onan generators, you can use regular oil or synthetic as long as it is made for the device and fits your budget.

According to the manufacturer of these generators, Valvoline Premium Blue 15W40 non-synthetic oil is the best option for an Onan generator. You may be surprised to find out that this is a diesel oil but it is the one that the company says to use and is the best option available.

To learn more about this topic, just continue to read our article. It explores this issue so you have the right information to protect your expensive generator. Take a few minutes to see how this information will help you keep your generator running at premium levels.

Onan 5500 Gas Generator Oil Type


If you are not looking at the brand or the type of oil, then you will want to use a 15W40 motor oil. This is the viscosity level you need in your generator. However, there are better brands and types of this oil available.

Some people use synthetic oil as it does not break down as easily as regular oil. But that synthetic type may be too expensive for some budgets. Brands only matter if you can tell the difference in the quality of the oil. If it is 15W40, then the brand is up to your preference and budget.

However, as you just read above, the company that makes Onan generators recommend the 15W40 non-synthetic, Valvoline Premium Blue oil. It may be made for diesel motors but that is what the company says should be lubricating your mechanical parts in your Onan generator.

Also, you may find out that there is now an Onan brand for oil. You can use that as well, as long as it is 15W40 and you have the money to spend. It is a little more expensive than regular motor oil.

Onan 5.5 HGJAB Oil Type


No matter what you do, you will get different opinions about which oil you should use. If you happen to use the wrong oil, the parts inside the generator may get damaged to poor lubrication.

For this model of Onan generator, some experts are saying you should use a 10W40 diesel engine oil IF you camp in mild to hot weather locations. They are also saying you can use Mobile 20W50 synthetic oil if you cannot find the regular option when you need to add more oil.

Other recommendations are:

Valvoline High Mileage With Maxlife Technology SAE 10W40

Castrol GTX High Mileage 10W-40

Formula Shell Conventional 10W-40

Havoline 10W-40 Motor Oil

Onan 5500 Generator Oil Capacity


For generators, the oil tank on this model of Onan generators is quite large. The tank can hold about 2 quarts of oil or about half of what a small car oil tank can hold. It is said that the 5500 is diesel-powered so you must use oil made for diesel engines.

When you are the changing oil on this generator, you should fill it up to the top of the dipstick. it is normal to see the oil near the fill cap when you are done. The oil filter does not last as long as car oil filters do. It is recommended that you change it every year for best performance.

Keep in mind that many people will recommend a 15W40 diesel motor oil for Onan generators. That is not wrong to use and may be the best option. When you camp in cold weather, you should go to a 5W30 viscosity to protect your engine.

Tips For Your Onan 5500 Generator Oil Change


You can talk to Onan owners to see what they say but be forewarned, the opinions and suggestions you get may be all over the map. When in doubt, call the company and see what they recommend.

Playing it safe is the best way to go, especially if your generator is still under warranty. Then, you can use any brand of oil that you want as long as it is a reputable brand that makes top-quality oil products.

As you are doing your oil change, make sure to get rid of all the old oil first. you do not want to mix old and new oil in your generator. Also, replace the filter at the same time. There is no point and nothing gained by running new oil through a dirty oil filter.

Finally, if you can afford it, use the recommended oil that we have talked about earlier. That is what the company says to use and when you are under warranty, it is best to use their recommendation. That is a way of protecting yourself from unnecessary expenses.

Download Onan 5500 Generator Service Manual


This link provides you with a variety of downloads and the Cummins Onan generators are a part of their supply. Just click here to get to the 5500 option. Then you can go to this website to get the same manual.

Those are just two options you can use. A quick search turned up quite a few places you can go to download a manual. If those places do not suit your preferences, call Cummins Onan to see if their website has a manual for you to download.

Some Final Words

Using the right oil is essential if you want your generator to last a long time. Also, you should do regular oil changes to make sure those mechanical parts are fully lubricated all the time.

While you are free to use any brand of oil you want, it is not always the best idea to do that when you are under warranty. Protect yourself by using the company-recommended brand. That way they have no excuse to deny your claim.

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