Can you Use Synthetic Oil in a Generator? (Portable & RV)

synthetic oil in generator

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From improving performance to increasing longevity, using synthetic oil in generators has a long list of benefits. But many deter from using synthetic oil to run generators because of some myths.

So can you use synthetic oil in a generator?

Synthetic oil is good for generators because of its superior cleaning power, heat tolerances, and resistance to breakdown. Synthetic oil can significantly improve your generator’s performance and make it last longer. However, not all generators can take the full benefits of synthetic oil.

In this post, we’ll give you more details on using synthetic oil in generators. We’ll talk about the benefits of synthetic oil, when and when not to use synthetics in generators, and finally, look at some synthetic oils for generators.

Read More: What type of oil does a generator use?

Can you Use Synthetic Oil in a Generator?

Yes, synthetic oil can be used in generators as they have a long list of benefits over conventional oil. However, synthetic oil shouldn’t be used to break in a generator or if the unit is old and worn down.

Synthetic oil has a high heat tolerance level making it ideal for small engines that run hotter compared to larger engines. This helps improve performance, increases the length of service, and requires fewer oil changes.

However, you shouldn’t run synthetic oil in generators that already have hundreds of hours of use with regular oil. Old or worn-out generators have larger gaps between the cylinder walls and the piston ring, which forces the sleek synthetic oil to leak.

Moreover, you should not use synthetic oil to break in your generator. Synthetic oil is more refined compared to regular oil which will increase the break-in time of the generator’s engine.

Can I Use Synthetic Oil in an Onan Generator?

Although Cummins Onan doesn’t recommend using synthetic oil in their RV generators, they don’t prohibit you from using it. According to Onan, synthetic oil has no long-term benefits for the additional cost.

However, synthetic oil is widely used by RV owners because of the benefits it provides. It significantly improves performance, keeps the engine clean and happy. 

The oil works exceptionally well with a wide range of temperatures, meaning you can go from winter to summer with the same oil and vice versa. By design, the oil is highly resistant to break down which means fewer oil changes.

Can you Use Synthetic Oil in a Portable Generator?

Irrespective of the brand or type of portable generator, synthetic oil is a perfect choice for portable generators. After the break-in period, synthetic oil can help keep your generator in top shape for years to come.

Generally, most camping generators come with small engines that run very hot compared to large vehicle engines. The excess from the engine breaks down convention oil quicker than synthetic oil.

Use the oil recommended by the generator manufacturer while breaking it in, then switch to synthetic. You will have a generator that will be by your side for years to come.

Why Use Synthetic Oil Instead of Regular Oil?

The fact is, every generator, be it portable or onboard RV, can use synthetic oil. Though some manufacturers don’t recommend it, your generator can still benefit from running synthetic oil.

Regular motor oil is made by refining crude oil. Additives are added to the oil to get it to the right viscosity, make it heat, and break down resistance. However, convention motor oil is not highly purified giving them an ununiform molecular structure.

On the other hand, synthetic motor oil uses a crude oil base that is further refined to produce a highly refined engine oil. The oil is engineered to be resistant to both temperature extremes. The uniform molecular structure allows the oil to reach even the tightest gaps inside the engine improving the engine’s service life.

Here are some benefits to using synthetic versus conventional oil.

Temperature Tolerances

Synthetic oil is designed to handle both weather extremes. Its manufacturing process allows it to be at an ideal viscosity irrespective of the weather.

Generators have small engines that run hot compared to large engines used in vehicles. An increase in load on the generator increases the engine RPM which further increases heat.

At higher temperatures, conventional oil break down readily, compromising their effectiveness. This increases heat and friction, resulting in engine damage and failure.

Synthetic oil, on the other hand, can tolerate much higher temperatures compared to regular oil, making them the perfect fit for generators.

Like extreme heat, synthetic oil can keep your engine protected in extremely cold temperatures. As the outside temperature drops, conventional oil thickens up making it difficult for the internal parts to move during startup.

However, because synthetic oil is specially engineered to handle extreme temperatures, it flows easily to reach even the tightest parts of the engine. Synthetic motor oil makes starting a cold engine effortless and safe.


Generally, a fully synthetic motor oil lasts longer compared to regular or synthetic-blend oil due to its ability to withstand heat. That means you have a big window between oil changes when using synthetic oil.

Because the oil breaks down slowly it retails its lubricating properties for much longer. This results in reduced friction and heat which helps extend the working life of the engine significantly.

Though synthetic oil is more expensive compared to regular oil, the need for fewer oil changes means lower costs in the long run. However, check the oil regularly and make sure to change your generator oil regularly.

On the other hand, you need to change your generator oil more frequently if you just switched from conventional to synthetic. This is because your engine may have a lot of gunk built up from the use of regular oil and needs to be drained frequently.

Superior Cleaning Power

Synthetic oil is well known for its ability to keep the engine clean. The refining process of synthetic oil removes the majority of the impurities from the crude oil, producing a cleaner oil.

The additives in the oil help clean existing gunk build-ups in the engine from using conventional oil. Synthetic oil can deep clean the internal parts of the engine as it can reach tighter spaces, extending the working life of the generator significantly.

Can Synthetic Oil be Mixed with Regular Oil?

Yes, you can mix synthetic and conventional oil in your generator without any issue. However, when regular oil is mixed with synthetic oil, it dilutes the synthetic oil reducing its benefits.

On the other hand, synthetic-blend motor oil is a mixture of regular oil with synthetic oil. A synthetic blend is prepared using the perfect ratio of both types of motor oil. This is not possible when mixing it yourself which can throw off the balance between the various additives in the oil.

When to Use Synthetic Oil in a Generator?

A full synthetic oil uses high-quality additives which protect the engine better compared to synthetic-blend or conventional oil. For this reason, synthetics are ideal for generators that will be used extensively and will put on hundreds of hours on it over time. 

Over time, the impurities from the convention oil will settle and deposit on the engine, reducing performance and service life. Switching to synthetic oil instead will reduce engine build-ups and clean up any existing sludge.

Synthetic oil is the best option for generators that will be used in places with harsh winters. Synthetic oil doesn’t change its viscosity as the temperature drops, making it easy to start the engine. Moreover, with the right oil viscosity, the oil will easily reach the vital engine components without any issue.

When Not to Use Synthetic Oil in a Generator?

Despite the many benefits synthetic oil offers, there are times you should use conventional oil over synthetics. Generators with hundreds of hours of runtime on regular oil have an increase in the gap between the piston ring and cylinder wall.

Because synthetic oil is sleek, it finds its way through those gaps and onto the combustion chamber, hindering performance. Thus, older worn-out generators should try to avoid running synthetic oil.

You can avoid running synthetics in generators that are used a few times a year. A full synthetic oil is more expensive compared to a synthetic blend or conventional oil. Thus using synthetic oil in such a scenario is a waste of money.

How Often to Change Synthetic Oil?

Generally, synthetic oil lasts longer compared to regular oil which means less frequent oil changes. However, this often depends on the brand of oil, working condition, temperature, etc.

Please follow the manufacturer’s recommendation for generator oil change intervals while the unit is under warranty.

However, brands like Castrol, Shell, Mobil 1, Valvoline have proven records to go longer between oil changes without any issue. They are also the top-of-the-line motor oil that will keep your engine happy and your investment secure.

Read More: How often to change generator oil?


Synthetic oil has a long list of benefits over conventional oil, making it ideal for small engines like generators. They help to keep the engine clean, improve performance, and increase its working life.

However, you shouldn’t run synthetic oil in generators that are worn out and have hundreds of hours of runtime under their belt. When choosing a synthetic oil, choose one from the top brand like Castrol, Shell, Mobil 1, Valvoline with proven track records.