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

Last Updated on by Matt

best oil for portable generator
When it comes to owning a portable generator, there are a few things you need to make sure that you maintain to ensure that you are getting the longest lifespan possible.

One of the most important things to check on your generator is the oil level.

Low oil level can cause major damage to your generator and using a low quality oil can run the risk of damaging vital engine components.

While there are many different oils out there to choose from for your generator, there are a few top tier choices that can help give your portable generator’ engine the best protection possible.

Today, I am going to talk a little bit about how oil works in your generator, what to look for in a generator oil, and I will suggest my top 5 generator oils.

What Does Oil Do For A Generator?

Before you start looking for different oils and try to figure out which one is going to be the best fit for your generator, you first 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 start to break down and be less effective. This can cause your engine components to be more susceptible to wear and tear.

Following to manufacturers engine oil change maintenance schedule 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 and industrial use.

Continuing their brand of 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

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 with no problems at all.

Generac can oil will also exceed 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 help to protect against the formation of sludge and varnish deposits.

This is a great benefit for generators as many tend to sit for awhile 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 their own line of oil to better supplement their engines. Honda engines are famous for lasting for 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 make sure to check and see if your specific motor doesn’t call for a certain oil before using it.

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

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 will exceed 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’ quality as they are used day in and day out both on the job site and 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
  • Provides maximum protection for engines
  • Reduces consumption and engine wear

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 will 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 be seen with thinner oil in larger generators. Once your oil becomes oxidized, it starts to lose the protection properties that helps to protect your engine.

Without proper protection, you can cause premature wear and tear to your generators engine.

The certifications of this oil are unclear as their 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’ 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 motor 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 help protect your generators engine from premature wear and tear.

Briggs & Stratton 30W Engine Oil - 48 Oz. 100028
  • The product is manufactured in United States
  • Warm weather formula for use in 40°-100° F temperatures
  • For use in all air-cooled 4-cycle engines

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 lawn mowers, snow blowers, and other small engine powered tools.

Creating an oil that meets all of the high quality demands that they are known for is no easy feat.

Briggs and Stratton puts all of their products through rigorous tests to ensure that they meet and exceed all of their standards that make their products high quality.

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.

This specific oil is going to be a synthetic oil, so you can expect some better performance when compared to conventional oil.

What makes this oil so great for your portable generator is that it has been specially formulated for air cooled, 4 cycle engine 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

This means you can use this for your generator, lawn mower, 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 owners manual for the manufacturer’s recommendations.

Just about every generator will have a preferred oil to use on 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 different 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 always 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 generators engine, that’s even better! When in doubt, you can always do a little research on the brand’s reviews.


When you take a look at the oil bottle across the shelf or even 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 that you need for your generator’s engine.


Another way that you can check for the authenticity of an engine oil is by looking for any type of ratings on the bottle. Most oil manufacturers are going to print any certifications and ratings that the oil has received to help give you a better understanding of 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 different types of oil that you can choose from with 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 your higher quality oils with different additives that make it perfect for higher mileage generators and engines that require synthetic oils.

It is usually on the more expensive side, but it is higher 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 with different brands of engines, there are a few things that you need to look for.

First, you need to 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 thy you need.

If your generator calls for a specific oil, you will need to ensure you 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 is one of the maintenance tasks that you should complete to ensure that your generator lasts for 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.

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

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

Generac Full Synthetic Motor Oil 5W-30






Easy of Use


Value for Money


Last update on 2020-07-04 Affiliate links & images from Amazon Product Advertising API

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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