Best Oil for Onan generator

You have just bought your shiny new Onan generator for your RV, and you are excited to get it going to start powering out all the devices on your RV. These will save you from shivering under the blankets when it is cold and freezing outside.

However, if it is the first time you are using a generator, things might start to get a little confusing. After all, how are you supposed to know what type of oil to use for your Onan generator, and what do all these labels on the different types of oil mean? Not all oils are the same, so if you want the best from your new Onan generator, read on and we will share some of our recommendations for the best oil to use with it.

The Basics of the Labels on Different Types of Oil

  • Viscosity

An important term to know in oil labelling is viscosity. In a nutshell, it is a measure of the oil’s resistance to flow. Most oils that are sold today are known as multigrades, which means that the oil falls into two different viscosity grades. An example would be a 10W-30. Here, the 10W means that the oil must have a certain maximum viscosity at low temperatures.

The lower the number coming before the letter “W” here, the better the cold temperature performance of the oil. The second number, 30, means that the oil has to fall under a particular viscosity limit at 100 degrees celsius. The lower the number, the thinner the oil is. Under the heat, motor oil thins out, while in the cold, it thickens.

  • Gasoline engine oil quality

Good quality gasoline engine oils fall under the following API performance categories- SJ, SL or SM. Under these different categories, the SM is of the highest quality.

  • Diesel engine oil quality

For diesel engine oil, the APA performance category is labelled under a different system. These include CF, CF-4, CF-4 and a few more. Here, CJ-4 is the best quality as of now.


Which Type of Oil

The very first, and probably the most important place to start from is to read the manuals that come with your Onan generator to see what types of oil are recommended for your particular generator. After all, different generators are built differently, and certain types of oil will be better to run in certain generators. As a general rule, choose a quality engine oil that is in the correct oil viscosity for your generator’s operating temperature, and refrain from trying to mix up a concoction of oils from different grades or brands.

  1. Briggs & Stratton 30W Engine Oil

Briggs is an extremely well established name in its field, so rest assured that they produce quality goods. It is also well reviewed by RV campers online, and is widely recognised as one of the best oils that can be used for smaller engines. One of the advantages of this oil is that it is specially crafted to work smoothly and without faults. It was also formulated to decrease chances of a breaking down on the air cooled motors (that can be found on portable generators).

This is integral when the operating temperature of the generator’s engine is high. Another benefit is that it is a detergent type generator oil that will help to prevent and deter harmful residue from building up inside the engine of the generator.

  1. Briggs & Stratton SAE 5W-30 Synthetic Small Engine Motor Oil

Here is another recommendation for a great oil to use for your Onan generator that is also manufactured by Briggs & Stratton. This oil is a bit different from the rest on this list, as it is a true synthetic oil. A benefit of using synthetic oils over conventional motor oils is that they are said to be able to lubricate the working parts of engines at a faster rate.

If you love taking your RV out in the winter months, this oil will be great for you too as it is a great cold weather oil. Synthetic oils are also better for the longevity of your Onan generator, as it results in less wear and tear in your generator engine when the engine starts to get hot. This is a great oil for devices with smaller engines, such as those in your Onan generator.

  1. Cummins 3265336 Onan SAE 15W-40 Oil

This oil here is sold by the very same company that produces the Onan generators, so you will never have to worry about the compatibility of it with your very own Onan generator. One downside to this oil is that it can get a little pricy, but if you are willing to fork out a little more, this is a great quality oil to get. Cummins has a long history in making a diverse range of high quality engines.

Their oils are tested extensively by professionals to make sure that they will maintain quality engine performance when they are used to fuel your generator. With such a great reputation, you know that the oil it sells you will also keep your generator engines running smooth.

This engine oil is manufactured to provide the most protection for your generator engine, and will reduce the wear and tear from friction on your engine, allowing you to enjoy using your generator for a longer time. With this oil, you will also find yourself having to top up the oil levels for your RV generator less frequently, as it is designed to lower oil consumption by your generator.

  1. Honda 08207-10W30 Motor Oil

I am sure all of you would have heard of this brand, as it is another reputable company in the business of quality small engines. The viscosity of this oil allows it to distribute itself throughout the engine rapidly. This will allow it to lubricate all of the parts of the engine to keep it from running dry, ensuring that it runs smoothly.

You should definitely watch out for this, as lower quality oils usually take more time to lubricate the engine of your generator, which can spell trouble for you and your Onan generator. This is another well reviewed oil, and many long term users of this oil have reported very few malfunctions in the engines of their equipment.

A few tips to make sure that your engine continues to run well

Besides making sure that you are using the right oil for your Onan generator, there is also more that you can do to keep your generator running smoothly for many years ahead. After all, a good quality generator is not exactly the cheapest thing you can buy out there, and you will want to keep it running well for many years to get your money’s worth. These are a few simple things that you can do to make sure that your generator is well cared for.

Firstly, it is a good habit to check the oil levels either every day or every 8 hours of use of your generator. To be safe, never check the oil when your generator is on and running, as hot oil can be thrown out of the dipstick hole. When the hot oil comes into contact with your skin, it can result in severe burns and a whole lot of unwanted pain that could very well ruin your RV trip.

Make sure that the oil levels are as close as possible to full, but never over fill it too. Overfilling can cause many problems such as foaming and engine shutdown, so take extra caution not to do that. To prevent any leakages, make sure that you screw back the cap tightly whenever you are re-filling the oil.

If you are taking a break from your RV journeys, make sure to take time to change the generator oil when you are back in your RV. The manual that comes with your Onan generator will indicate the recommended intervals for changing the oil in the generator. A useful tip will be to warm up your generator before draining the old oil inside, as it will flow out faster if you do so. If possible, try to run your generator periodically to prevent the building up of deposits.

It is also recommended for you to opt for genuine Onan replacement parts when you are looking for a change in your oil and fuel filters instead of those generally sold on the market. While these genuine replacement parts might be a little pricier, you know that they have been designed specifically for your Onan generator, and will maximise both the power output and lifespan of your generator. Choosing to use aftermarkets parts will also mean that any damage caused to your generator by their use will not be covered by the warranty that comes with your generator.

We hope that with all this new information, you will be able to make better choices for the oil to use with your Onan generator. Starting with the ones recommended here is never a bad option, and you will find the best oil for your needs along the way!