Best Oil for a Generac Generator (& How Much Oil to Use)

When using a Generac generator, several maintenance practices ensure that it gets a longer lifespan. For instance, a low oil level in the generator can cause severe damage, while using poor quality oil risks damaging key engine components. 

Even though there are a variety of oils to select from for your Generac generator, you should go for a top-tier choice to provide your portable device’s engine with the best protection. The best oil is one that provides efficient performance at an affordable cost. 

Here, we look at the best oil for a generator and how much oil you need to use. 

Which Oil Is Best for Generac Generators?

Even though there are many products on the market, there are quality and effective oils that you can use in your Generac generator or any other portable product. Below are some of the available products:

1. Generac Full Synthetic Oil 5W-30

Generac is among the top brands in the industry. The company has developed its line of generator oil for use in its products. Generac is reputable for developing high-quality generators of all applications, including for industrial and home use. 

Their full synthetic generator oil is meant to continue the company’s high-quality brand. Even though the oil is made specifically for Generac generators, you can still use it with other brands. Generac developed the oil to offer generator users the correct oil to apply in their engines when it’s time to change the oil. 

The oil is fully synthetic, meaning that it’s a high-performance oil that is guaranteed to increase the lifespan of your generator. The product is developed with a viscosity of 5W-30, which is similar to that of vehicle engine oil. 

It means that you can apply it in both summer and winter without experiencing any challenges. Generac oil exceeds all SN and API service classification requirements. Even though it’s a common feature in most products, it’s worth mentioning since most users look for the rating on their oils. 

The materials used to make Generac oil protects against the formation of varnish and sludge deposits. It’s a great advantage for generators since many products sit for long periods without use. 

The high-quality base is fortified with an advanced additive for effective performance. It’ll also offer maximum protection against any viscosity breakdown. 

2. Honda 08207 10W30 Oil

Honda is another brand that manufactures its oil to supplement its engines. Honda engines and other engines that use this oil are reputable for having an extended lifespan beyond their expected lifespan. One critical component of the extended lifespan is the high-quality oil employed in the engines. 

The Honda 08207 engine oil is a top-quality product that you can employ in any gasoline-powered portable generator. The engine you apply this product in should be calling for a 10-30. 

The product is designed with a viscosity of 10-30, which is thicker than the Generac product but will still offer quality performance in all weather conditions.

It means that regardless of where or when you use the generator, there is no need to worry about switching out the oil to take care of the weather. 

The Honda oil exceeds all the requirements for SM and API service classification. It comes with a unique blend of the best-quality top stock and shear stable polymer additives. 

3. Cummins 3265336 SAE 15W-40 Oil

Cummins is another top company specializing in engine manufacturing. The company is reputable for producing diesel engines in most new dodge pickup trucks. The powerful engines provide proof enough that Cummin has invested in quality. 

Cummin developed their line of engine oil to keep most engines running for extended periods. The oil is effective at reducing tear and wear on critical engine components. 

With the Cummins engine oil, expect to get a 15W-40 product that is thicker than most products on our list. Apart from protecting generators against wear and tear, the product is designed for application on RV generators.

Even though you can employ the oil on several generator brands, the product is ideal for larger-watt generators that need thicker oil for effective protection. The oil is designed to be thicker than other available products to reduce the loss of oil due to oxidation, which is common with thinner oil. Once the oil is oxidized, it’ll lose its protective properties. 

With poor protection, your generator’s engine will be exposed to premature wear and tear. You can use the oil on any other generator, including Generac engines. 

4. Briggs & Stratton 30W Oil

There is no argument that Briggs & Stratton is among the industry’s most reputable manufacturers of small engines. You can find the company’s motors on most products, including go-karts, lawnmowers, and portable generators

To protect their engines, the company has created Briggs & Stratton engine oil to protect the engine from premature tear and wear.

Briggs & Stratton’s oil is available in viscosities of 30W to enable you to apply it through all seasons. It makes the oil ideal not only in portable generators but also snowblowers and small engine-powered tools. 

Briggs & Stratton is known for putting all the products through rigorous tests to meet the required standards. 

The oil has received approval from Briggs & Stratton engineers to exceed or meet the need for 4-cycle engines. The oil is also a high-quality detergent classified by the API as SJ/CD. 

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

Similar to the Briggs & Stratton 30W, the SAE 5W-30 oil is another reputable option for any portable generator. Since it’s synthetic oil, you can expect better performance than conventional oil. 

What makes the oil effective for portable generators is that it’s formulated for air-cooled, 4-cycle engines. Apart from using the oil for your portable generator, you can also use it in lawnmowers and other engine-based power equipment. 

The oil is blended to Briggs & Stratton factory specifications and is warranty-approved to ensure that your portable generator functions for a longer time. 

It comes with a viscosity of 5W-30, meaning that you can use it year-round without worrying about whether it’s too thin or too thick. 

How to Select the Best Oil for Your Generac Generator

If you want to get the right oil for your Generac generator, consider the factors below: 

1. Read the Manual

Reading the manual is the best step that you should consider while purchasing oil for a Generac generator. At least every portable generator comes with a user manual or guide. 

A section in your manual about generator maintenance talks about how you need to take care of your generator and the kind of oil that the engine requires. 

2. Determine the Type of Engine

Different types of engines require you to employ different oil types. Since most of the generators are designed with 4-stroke engines, the choice becomes easier. It’s difficult to find generators having 2-stroke engines. 

SAE30 is the most common oil used in 4-stroke engines found in Generac generators and other related equipment. There is also an option of going for synthetic variations such as SAE 10W-30 and SAE 5W-30. 

3. Check the Operating Temperature

If you plan to run your Generac generator out in the cold, this is a criterion you should consider. Some oils are designed to be employed in extreme temperatures. Others support a variety of temperature ranges. 

For instance, SAE 5W-30 is perfect for Generator engines exposed to temperatures as low as -20 degrees Fahrenheit. 

4. Take Note of the Viscosity

Temperature is one feature that determines how ideal a specific oil type is to support cold weather. It also represents the resistance of oil to flow. You can determine the viscosity of oil by simply checking its name.

The number before “W” represents the viscosity of the oil at 0 degrees Fahrenheit. The second number stands for viscosity at 212 degrees Fahrenheit. 

In the case of hot temperatures, the higher the oil’s second number is, the better it is. A higher number means that the oil is thicker and offers improved lubrication for the moving parts of your generator engine. 

If you want to employ your Generac generator at a cold temperature, you should pay attention to the first number. For the above reason, SAE 5W-30 is the perfect option for sub-zero temperatures. 

5. Stick To Reputable Oil Brands

It would help to purchase oil that a reputable company develops. The products or brand should be approved by SAE (Society of Automotive Engineers). Some top brands worth considering are Shell, Schaeffer, Castrol, and Generac. 

Check out the product you want to purchase on Amazon so that you only go for a product that has positive reviews. 

How Many Quarts of Oil Does a Generac Generator Need?

The capacity of a Generac engine ranges between 1.1 to 1.9 quartz based on the size. However, you must change a Generac oil at least every two years or 200 hours, whichever comes first. A CorePower 7kW generator’s oil should be changed at least every 100 hours or one year. 

Below are steps to follow to change the oil in your Generac generator:

  1. Start your generator and operate it until it becomes warm.
  2. Turn off your generator and then remove the oil drain hose from the spring-loaded mounting clip. 
  3. Remove the cap from the drain hose and allow the oil to drain into a container. 
  4. Replace the cap at the drain hose and return it to the mounting clip. 

Can You Use 5W30 Instead of 10W30 Oil In Your Generator?

You can use your 5W30 oil in place of the 10W30 oil in your Generac generator. The two products have the same viscosity, meaning they’ll offer the same performance when they reach the operating temperature.

Selecting the best oil is critical if you want to get the most out of your generator, save some money, and extend the generator’s lifespan. However, it can be confusing, especially if you visit your local garage only to find that they have a random selection of oil. 

A question arises of whether you can use a certain type of oil in place of another. Can you use 5W30 instead of 10W30?

  • 5W30: The oil is more fluid at lower temperatures making it easier to start a cold engine. It’s recommended for use at temperatures between -31 degrees to 35 degrees celsius. The product flows faster and is more fuel-efficient. 
  • 10W30: Even though it’s still fluid, it’s thicker than the 5W30 making it harder to start your engine. It’s recommended for use between -25 to 35 degrees celsius. The product offers better sealing action and is less fuel-efficient. Heavy-load generators must use it. 

What The Numbers Mean

  • 5: The first sequence of the number before W represents the product’s viscosity at low temperatures. 
  • W: The letter represents the winter and differentiates the oil’s viscosity at hot and cold temperatures.
  • 30: The numbers after W represent the oil’s viscosity at a higher temperature. 

The main difference between the 5W30 and the 10W30 oil comes down to viscosity. Viscosity refers to the thickness of the oil and the ability to flow. The 10W30 is thicker than the 5W30 product.

A lower number means that the oil is more fluid. A 5 will pour more easily than a 10. It, therefore, tells you how quick the oil will get to the engine and other internal components. 

An increased viscosity means that your oil will be more sticky and adhere to the mechanical components better, thus lubricating better. It becomes even better with an increase in pressure and stress on the system. 

When the oil is too thin, it becomes less helpful to your engine. 

When Should You Apply the 5W30 and 10W30 Oil?

When settling on the type of oil to use, you need to consider how quickly the oil flows. Since the 10W30 is thicker, it’ll move more slowly than the 5W30. 

Since the two have almost the same viscosity, they’ll precisely function the same way when they reach operating temperature. However, where circumstances are similar, the 5W30 product will start up your car faster. 

If the oil’s viscosity is lower, it can easily fly off your engine components and cause metal-to-metal contact, thus reducing the engine lifespan. If you want to improve the lifespan of your generator, select an oil product with a thicker viscosity. 

However, there are also other considerations to put in mind. For instance, the 5W30 product is more effective during cold months. You can use the 10W30 during warmer months. If the temperature increases, you can consider the 15W40 product. 

Is It Possible to Mix 5W30 and 10W30 Oil?

Do you think it’s safe to mix the different grades? Yes, mixing two grades of oil is just and won’t lead to any damages to your generator. 

There is a chance that you have ever mixed different oils before without even realizing it. Since the main difference between the 10W30 and 5W30 is viscosity, it’ll not cause any major differences to your generators. One type is more viscous while the other will reach the engine quicker. 

However, mixing the different grades of oil reduces the longevity and economy of your generator engine. It should also worry you to mix regular and synthetic oil. 

Can You Use SAE 30 Instead of 10W30 Oil in Your Generator?

You can use the SAE30 oil in your generator instead of using the 10W30. 

However, there are various things you need to consider, including the engine temperature. 

The 10W30 products are for modern engines, while older engines use the SAE30 products. The SAE30 is perfect for warmer temperatures, while the 10W30 is ideal for varying temperature ranges and in cold weather.

Is a Low Viscosity Oil Beneficial?

As we have seen, the “W” in 10W30 stands for winter, meaning that the oil can withstand cold temperatures. It means that the low viscosity oil that falls into the category is a perfect option for cold winter seasons. 

A thinner oil flows efficiently and is thinner. Any generator oil acts as a lubricant for its engine. It’s therefore critical for the effective performance of the generator. 

For the generator engine to function effectively, the engine should find the right balance when it comes to the thinness of the oil. The oil needs to flow efficiently when the engine is cold and retain enough oil when the engine heats up. 


If you own a Generac generator, there are various top oil products that you can employ to offer its engine effective protection. The best oil is one that offers effective performance at an affordable cost. 

It’s important to understand that a Generac engine has a capacity range of 1.1 to 1.9 quart based on its size. 

Before you purchase any oil brand for your Generac generator, it’s important to consider the factors highlighted above, such as determining the engine type and the operating temperature. Ensure that you read the instruction manual strictly if you want to get effective outcomes. 


Hubert Miles

I've been conducting home inspections since 2002. I'm a licensed Home Inspector, Certified Master Inspector (CMI), and an FHA 203k Consultant. I started to help people better understand whole-house and portable generators.

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