What Is The Best Oil For An Onan Generator? [Inc. 4000 & 5500 Models]

If you own an Onan generator, you'll want to know the best oil to use on it. Fortunately, we did the research for you, and here is what we found.

SAE 30W viscosity oil is ideal for your 4000-model Onan generator. However, it is best to get SAE 10W-40 for the 5500 model.

It is crucial to use the recommended oil for your Onan generator. Please keep reading to get detailed information about the Onan generator and the best oil to use. 

What Is The Best Oil For An Onan Generator? [Inc. 4000 & 5500 Models]

Onan is a leading producer of generators for recreational vehicles (RVs) and campers. And the 4000 and 5500 models are currently the most sought-after.

A man pours gasoline into a generator on the doorstep.

Onan generators are of high quality. You can expect them to last a long time if they are well-maintained and operated with the right oil.

The summer grade SAE-30 oil is suitable for the Onan generator. However, the best oil to use on your generator depends on the climate where you live or plan to travel. 

RV owners who spend their winters traveling through states with colder temperatures will require a specific kind of generator oil.

Generally, this oil is not the same as the type those who spend most of their time in places with higher temperature use. The variation arises due to a difference in viscosity - a measurement of its resistance to flow.

Please note that oil loses some of its thickness when heated and regains it when it cools. So, it is vital to consider the prevailing temperature conditions when selecting a suitable oil for your generator. Additionally, you need to consider your generator's model.

Best Oil For Onan 4000 Generator

Motor oil canister on white isolated background.

Because Onan generators are not manufactured the same way, the type of oil they require is also different.

Using the wrong oil may lead to insufficient lubrication in the generator's motor. Hence, you must ensure you get the right oil for your Onan generator model.

For a 4000 Onan Generator, the temperature of the environment in which you will be operating the vehicle matters. You can use a 30W oil in locations where the temperature is at least 32 degrees Fahrenheit higher.

You can switch to a 15W40, a 10W30, or a 10W40 as the temperature drops. But when the temperature drops to an exceedingly low level, you should use a 5W30.

Oils of the highest grade will invariably be SAE-approved and rated - it is not advisable to use oils that are not rated.

Click here to see this SAE 30W viscosity oil on Amazon

Best Oil For Onan 5500 Generator

view of castrol engine oil display on the supermarket shelf.

To get the most out of your Onan 5500 generator, you should use 10W40 oil in regions with temperatures ranging from mild to high. 

Even though 10W40 is the recommended oil for the Onan 5500 generator, several users have reported success with Mobil1 20-50 synthetic oil. Still, it is best to stick with 10W40 oil unless it is unavailable.

Click here to see this SAE 10W-40 viscosity oil on Amazon

How Often Should You Change The Oil In Onan Generator?

Most models need an oil change after 100-200 hours of use. The Onan generator owner's manual suggests replacing the oil once every year or every 100 operating hours. But if you just got a new RV generator, you should change the oil after the first 50 hours of use.

Changing the oil is a quick and easy task that takes less than an hour. The process is similar to changing the oil in a lawnmower or a car. It is advisable to change the oil filter when changing the oil. You can also top off the coolant.

How Do You Change The Oil In Onan Generator?

Auxiliary Electric Power Diesel Generator Emergency Equipment. - What Is The Best Oil For An Onan Generator? [Inc. 4000 & 5500 Models]

Before changing the oil in your Onan generator, the first thing to do is get the necessary materials ready. You should get the right oil, a T30 Torx bit, an oil pan, and a 12mm socket. When all these are ready, you can proceed with the following steps:

Step 1: Warm The Generator

To begin, turn on your generator and leave it to warm for about 5 minutes. When the generator is warm, you can proceed to the next step.

Step 2: Remove The Old Oil

Take out the oil-drain plug protection plate to do this. You can use your T30 Torx bit for this. Next, use the 12mm socket to remove the oil drain plug.

Position the oil pan well so the oil can drain into it. After that, reinstall the drain plug but leave the protector plate uninstalled.

Step 3: Pour In The New Oil

After removing the old oil, pour in the Onan-approved oil, then turn on the engine. It is always advisable to inspect the drain plug for leaks. If there is none, turn the generator off and install the protector plate. 

Next, use the dipstick to check if the oil is at the right level. Don't forget to clean any spilled oil and appropriately dispose of the old oil.

You can also use the opportunity to inspect the air filter. Additionally, refer to the owner's manual to determine if your generator requires more steps. 

How To Reset An Onan Generator After Oil Change

To ensure that your Onan generator continues to work correctly after an oil change, take these steps to reset it.

  1. Turn off your Onan generator. To shut down the generator, enter the command "off" and press enter. It is not hard to spot the enter button on the generator. You should turn it off manually if your generator's power switch is missing.
  2. Let it sit for 30 seconds.
  3. After 30 seconds have passed, start the generator manually. Then, test it by operating it for five minutes.
  4. Turn off the generator again. Allow thirty seconds to pass and ensure the generator is turned off fully. The generator should now be set to automatic mode. 

How Many Quarts Of Oil Does An Onan Generator Take?

Mobile diesel generator for emergency electric power use for outdoor

The kind and model of Onan generator you own determines the number of quarts required. When changing the oil in your Onan generator, you should always use a dipstick to determine the generator's current oil level.

Generally, generators are not good at storing oil, so your generator can consume 1 quart every 50 hours. But this can vary based on the model of your generator. Some may use just 1/2 quart every 75 hours. However, your generator will likely use up more if you use a very thin oil.

An Onan 4000 generator requires 1.6 quarts of oil. The Onan 5500 generator, on the other hand, can take two quarts. It typically takes up about one-half as much space as the oil tank in a compact car does.

When filling the oil tank in your generator, you must fill it to the top of the dipstick. When it is full, you should be able to see oil near the cap. However, ensure that you do not overfill the oil.

Does An Onan 4000 Have An Oil Filter?

Onan has developed several unique enhancements for its generators over the years. They have focused a lot of energy on simplifying RV upkeep for the average consumer. As a result, the Onan 4000 generators are built and engineered so that they do not have an oil filter installed.

That said, it is essential to remember that the Onan 4000 collection comprises more than one model. So, some models, such as the Onan 4000 Genset, come with an oil filter.

The maintenance of the Onan 4000 models that don't have an oil filter is easier. But the absence of an oil filter in some Onan 4000 generators stresses the importance of using the right oil. Also, you should change the oil in these generators regularly and avoid running them when they still have old oil.

Can Low Oil Cause Onan Generator Not To Start?

If the oil in your Onan generator becomes too low, the engine may not start. While older generator models can start with low oil, the modern models contain a "low oil shutoff sensor" that will prevent the engine from starting if it detects a low oil level.

So always check the generator's oil level and add more when required.

To Wrap Up

When you use the appropriate oil for your Onan generator, it performs optimally and lasts longer. It is advisable to use SAE 30W viscosity oil to keep your 4000-model generator running well. If you have the 5500 model, it is best to use SAE 10W-40. 

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