Best Oil for a Portable Generator (Top 5 Highest Quality)

Last Updated on September 14, 2020 by Scott

best oil for portable generator
When it comes to owning a portable generator, there are a few necessary maintenance routines to ensure that you get the longest lifespan possible.

One of the most important things? Check your generator’s oil level.

Low oil level can cause major damage to your generator, and using a low-quality oil risks damaging vital engine components.

While there are many oils to choose from for your generator, select top tier choices can give your portable generator’s engine the best protection possible.

Today, I am going to talk about how oil works in your generator, what to look for in a generator oil, and my top 5 generator oil suggestions.

What Does Oil Do for a Generator?

Before you try figuring out which oil will best suit your generator, you need to know what the oil does for your generator.

Gasoline portable generators utilize engines that require oil to run properly.

These engines use oil to lubricate the rotating assembly inside the engine to ensure that the moving metal pieces have a smooth, less resistant path.

This reduces engine wear and keeps your engine lasting for years to come.

Over time and with many uses, this oil can break down and become less effective. This can make your engine components more susceptible to wear and tear.

Following the manufacturer’s maintenance schedule for oil changes can greatly prevent any unwanted engine damage.

5 High-Quality Engine Oil I Recommend

1. Generac Full Synthetic Motor Oil 5W-30

As one of the biggest names in the generator industry, Generac has developed their own line of engine oil to use with their generators.

Generac is well known for providing high-quality generators for all types of applications, from home use to industrial use.

Continuing their brand’s high-quality offerings is their full synthetic engine oil, made specifically for Generac portable generators.

This oil was developed to provide Generac generator owners with the correct oil to use when it comes time for an oil change.

Generac Full Synthetic Motor Oil 5W-30 SN Quart Bottle Part# 0J5140 (qt) 2-Pack
  • Generac SYNTHETIC OEM Oil (2 Quarts)
  • High quality synthetic base fortified w/ an advanced additive
  • Oil absorbent pad to prevent spilling on floors and other surfaces

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This specific oil is going to be fully synthetic which means it is a high-performing oil that is sure to keep your generator lasting longer.

It had a 5w-30 viscosity which is similar to vehicle engine oil.

This means it can be easily used in both winter and summer without problem.

Generac oil also exceeds all API and SN service classification requirements. While this is a common feature in most oils, it is worth mentioning as most people look for this rating on their oils.

The materials that make up this specific oil protect against the formation of sludge and varnish deposits. This is a great benefit for generators as many sit for long stretches without use.

The high-quality synthetic base is fortified with an advanced additive for optimum performance. It will also provide maximum protection against viscosity breakdown.

2. Honda 08207 10W30 Motor Oil

Honda manufactures its own line of oil to better supplement their engines. Honda engines are famous for lasting years past their expected lifespan, and one of the key components to this extended life is the high-quality oil used in these engines.

This Honda 08207 engine oil is a high-quality Honda oil that can be used in any of their gasoline-powered portable generators.
Of course, this oil can be used in just about any Honda or similar engine that calls for 10-30; just check and see if your specific motor doesn’t call for a certain oil before using this.

Honda 08207-10W30 PK2 Motor Oil
  • Genuine OEM Honda Part
  • Package Quantity: 2
  • SAE 10W-30

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The viscosity of this oil is going to be 10-30, which is a little thicker than the Generac but will still provide excellent performance in all weather conditions.

So no matter when or where you use your generator, you will not have to worry about switching out your oil to cater to the weather.

This Honda oil exceeds all requirements for API service classifications SM and all new Honda power equipment.

It has a unique blend of sheer stable polymer additives and some of the best-quality top stock.

3. Cummins 3265336 Onan SAE 15W-40 Oil

Cummins, a leader in engine manufacturing, is best known for their Diesel engines in many newer Dodge pickup trucks.

These powerful engines are a testament to Cummins’s quality, used day in and day out both on the job site and in cross country driving.

To keep these engines running as long as possible, Cummins has developed their own line of engine oil to help reduce wear and tear on your viral engine components.

Cummins 3265336 Onan SAE 15W-40 Oil - 1 Quart
  • 32 oz. factory tested oil
  • Reduces consumption and engine wear
  • Provides maximum protection for engines

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With the Cummins 3265336 engine oil, you can expect to get a 15w-40 weight oil, which is the thickest oil on my list.

This thick engine oil is designed to provide maximum protection against wear and tear and is designed to be used on RV generators.

While you can use this oil on many other generators, it is best used on larger watt generators that require a thicker oil for better protection.

One of the main reasons that this oil is thicker than most on this list is to reduce the loss of oil to oxidation that can happen with thinner oil in larger generators. Once your oil becomes oxidized, it starts to lose the protective properties you need.

Without proper protection, you can cause premature wear and tear to your generator’s engine.

The certifications of this oil are unclear as there is a lack of information about this oil online, but if it is safe to use on Cummins engines, you can expect that it exceeds the Cummins’s standards and expectations.

4. Briggs & Stratton 30W Engine Oil

It goes without saying that Briggs and Stratton is a widely-known manufacturer in the small engine industry.

After all, their motors can be found on anything from go-karts to lawn mowers and, of course, portable generators.

To help better protect their small engines, they have developed Briggs and Stratton-specific engine oil to protect your generator’s engine from premature wear and tear.

Briggs & Stratton 30W Engine Oil - 48 Oz. 100028
  • Tested and approved by Briggs & Stratton engineers
  • Warranty certified and recommended in all Briggs & Stratton manuals
  • A high quality detergent oil classified SJ/CD by the API

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This specific Briggs and Stratton oil is going to come in a 30w viscosity so that you can benefit from an all-season oil.

This makes it perfect to use not only in your portable generator, which may see a lot of use in the winter when blackouts are more common, but also your lawnmowers, snowblowers, and other small engine-powered tools.

Briggs and Stratton puts all of their products through rigorous tests to meet and exceed all of their standards.

In fact, this oil has been approved by the Briggs and Stratton engineers to meet or exceed the demands for 4 cycle engines.

It is also a high-quality detergent oil classified SJ/CD by the API.

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

Much like the Briggs and Stratton 30W, this SAE 5W-30 engine oil is another great choice for your portable generator.

Specifically, this is synthetic oil, so you can expect better performance compared to conventional oil.

What makes this oil so great for your portable generator is that it has been specially formulated for the air-cooled, 4-cycle engines found in outdoor power equipment.

Briggs & Stratton SAE 5W-30 Synthetic Small Engine Motor Oil - 32 Oz. 100074
  • 100% Synthetic SAE 5W-30
  • For Use In All Air Cooled 4-cycle Engines
  • 32 Oz. bottle

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This means you can use this for your generator, lawnmower, and other engine-equipped power equipment.

This engine oil has been blended to Briggs and Stratton factory specs and is warranty-approved to ensure you keep your engine running for as long as possible.

If you are using a Briggs and Stratton engine on your generator, this is going to be the oil to use.

With a 5w-30 viscosity, you can use this oil year-round with no worries of it being too thick or too thin.

What to Look for in a Good Engine Oil

The first thing that you should do when choosing an oil for your generator is checking your owner’s manual for the manufacturer’s recommendations.

Just about every generator will have a preferred oil for their specific engine to coincide with the warranty.

If you no longer have the manual, there are certain things that you can look for before making a purchase.


Shopping for oils for your generator can be quite intimidating as there are many types of oils to choose from.

One thing that you can always look for is name brand oils. Popular name brands of oil are usually going to be the higher-quality oils as they have a reputation to maintain.

If you can find the same brand of oil to match your generator’s engine, that’s even better! When in doubt, research the brand’s reviews.


When you look at the oil bottle (or specs online), one of the first things you are going to see is the viscosity. Viscosity is the measurement of how easily the oil pours at a specific temperature.

Thinner oils are going to have a lower viscosity and will be easier to pour in cold temperatures. Thicker oils will have a higher viscosity and will pour slower in cold temperatures.

Refer to your user manual for the proper viscosity for your generator’s engine.


Additionally, you can check for the authenticity of engine oil by looking for any type of ratings on the bottle. Most oil manufacturers will print any certifications and ratings that the oil has received to further prove the quality of the oil.

You can also check online for any reviews of the oil to see how other customers like it.

Conventional vs. Synthetic

There are a few types of oil you can choose from, the most popular being conventional and synthetic.

Conventional oil is going to be your everyday, standard oil that can be used in most applications with low miles.

If your engine is fairly new and does not require synthetic, conventional can be used and is a great, budget-friendly option.

Synthetic oil is going to be higher-quality, containing additives that make it perfect for higher mileage generators and engines that require synthetics.

It is usually on the more expensive side, but it is higher in quality.

Frequently Asked Questions

oil bottles

Can I use a different brand oil than my generator’s motor?

When it comes to mixing brands of oil and brands of engines, there are a few things to look for. First, check to see if your generator calls for a specific brand of oil or just a certain weight.

If it just says a weight, you can most likely get by with any top tier brand oil in the viscosity you need. However, if your generator calls for specific oil, stick to the manufacturer’s recommendations. When in doubt, give the generator manufacturer a call.

How often should I change my generator’s oil?

Changing your generator’s oil ensures that your generator will last as long as possible. When it comes to oil change intervals, you will need to reference your generator’s manual for the correct maintenance schedule.

On average, plan to change the oil every 50 hours of run time.

Many generators have a run time meter, but for those that don’t, you will need to keep track of the hours manually.

Generac Full Synthetic Motor Oil 5W-30






Easy of Use


Value for Money


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One comment

  1. Since portable generators run at 3600 RPM or so they got the nickname of “screamers”. That being the case I thought best to use Valvoline VR1 racing oil. After 9 years it still starts easy and runs well even running in 100 degree + heat for extended periods. Just my .02 worth.

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