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The best oils for generators

Are you looking for a new oil for your generator but have no idea how to choose it? Are you wondering about what kind of oil does a generator take? Then take a detailed look at our comprehensive shopping guide. Besides tips and features to look for, you will also learn about the best and most reliable brands of oils we recommend.

Best oil for generator

Best choice

Quaker State Heavy Duty SAE 30 Lubricant Motor Oil

These oil is designed for a consistent wear and viscosity protection throughout the service life of the oil. It is specially formulated for working in air cooled motors like portable generators are. The oil contains also detergent to constantly wash the engine from inside and keep the harmful residue from building up in the engine.

4,9 Rating
Meets or exceeds API SN and prior API SM, SL, SJ service categories
HD motor oil contains acid neutralizing additives to stop combustion acids from corroding your engine

Top rated oil for generators

Top choice

Briggs & Stratton SAE 5W-30 Small Engine Oil

4,8 Rating
For use in all air cooled 4-cycle engines. Classified SJ/CD by the API
Approved by Briggs & Stratton engineers & recommended in all operator manuals

More Information

Best choice

Quaker State Heavy Duty SAE 30 Lubricant Motor Oil

4, 9 Rating
Meets or exceeds API SN and prior API SM, SL, SJ service categories
HD motor oil contains acid neutralizing additives to stop combustion acids from corroding your engine

More Information


Pro Honda GN4 4-Stroke Motor Oil 10W-30

4,7 Rating
Has better shear-resistance, viscosity stability and cleanliness
Specifically designed for the unique requirements of motorcycle engines

More Information

Oil for generators

The best oils for generators

Choosing Engine Oil for a Gasoline Generator

Gasoline engines are divided into two-stroke and four-stroke

Two-stroke engines do not have a separate sump for oil: the carburetor is filled with an oil-gasoline mixture. That’s why special requirements are imposed on the oil for two-stroke engines: in addition to its lubricating properties, it has to dissolve in gasoline and burn as completely as possible. No problem with the choice here: buy a special oil for air-cooled two-stroke engines – the 2T standard. Not to be confused with TS-W3 oil – it is for water-cooled engines (outboard boat motors, jet skis).

Let’s move on to the four-stroke engines. The choice here is much bigger.

There are two main classifications of engine oils:

  • by viscosity (SAE)
  • on a set of performance properties (API).

SAE informs about the ambient temperature, in which oil will work best, lubricating all the nodes. This standard divides engine oils into six winter grades (OW, 5W, 10W, 15W, 20W, and 25W) and five summer grades (20, 30, 40, and 50). A double number indicates an all-season oil (5W-30, 5W-40, 10W-50, etc.).The most universal SAE oil for warm seasons will be 10W30. So if you see SL 10W30 on the label – you can take it. When using an alternator in the cold season, pay attention to the SJ or SL marking, these are the most modern and high-quality oils for gasoline engines.

Oil change has a certain interval, which is prescribed for each generator in its technical passport, but there are cases where the documentation is not always available or the passport may be in a foreign language. For example, you are unlikely to find a recommendation to run-in there. Meanwhile, it is very important for the normal operation of your plant.

Tips for changing the oil:

  1. If the product is new, the first change should be after 5 hours of operation. This is the “running-in” I was talking about. The new parts sort of “lapping” into each other, smoothing out the micro-irregularities. The oil absorbs all metalized particles, it becomes waste – black and murky. This consistency has to be necessarily drained and changed;
  2. The second change takes place (on average) – after 20-25 hours of operation. This is the optimal replacement interval, regardless of what loads the generator was dealing with;
  3. I recommend a third oil change after 50 hours of operation.

Subsequent changes can be made at intervals of 50 or 100 hours, depending on the manufacturer or the engine installed on the alternator. I recommend that you clearly adhere to the specified interval in the data sheet of the generator itself.

Best oil for small engines

1. Quaker State Heavy Duty SAE 30 Lubricant Motor Oil-1

2. Briggs & Stratton SAE 5W-30 Synthetic Small Engine Motor Oil – 32 Oz.

3. Cummins Power Generation Motorhome Trailer RV and Automotive Engine ONAN SAE 30W Oil

4. Pro Honda GN4 4-Stroke Motor Oil 10W-30 32 oz.

What is the best oil to use in a generator?

A portable gas generator can be a very important tool in your household. Usually these generators are purchased for a sudden knock out of electricity due to e.g. severe weather conditions. This portable gas generator is an important part of your camping trip planning. Like any other complicated mechanical device it needs to a regular check of its functions and it needs a correct maintenance to ensure this thing is running. Read also article: motor oil for lawn mower

Engine oil is one of the most important items to check, the proper model of oil, the regular oil change and checking the oil level is vital for the functioning of an engine.

Not all generator oils are equal good and here we try to find out, what oils to look first at when looking for oil to change in the engine.

How to Choose the Best Oil for Generator

1. Quaker State Heavy Duty SAE 30 Lubricant Motor Oil-1

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These oil is designed for a consistent wear and viscosity protection throughout the service life of the oil. It is specially formulated for working in air cooled motors like portable generators are. This property of oil is very important when your engine has to deal with high engine operating temperatures. The high temperatures are are an often case here. The oil contains also detergent to constantly wash the engine from inside and keep the harmful residue from building up in the engine.

Test results from independent laboratory show that HD motor oils saves engine with 3 times better wear protection.

The most important features of the oil are: the Quaker State HD motor oils are engineered to reduce wear and protect against high temperature and severe service operation; This motor oil meets or exceeds API SN and prior API SM, SL, SJ service categories; HD motor oil contains acid neutralizing additives to stop combustion acids from corroding your engine; HD Motor Oil used oil (standard oil for the vehicle), still passed the Industry wear requirements; provides a constant grade in viscosity throughout the oil service life.

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

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Synthetic oil provides a better wear control of an engine, even under heavy operating conditions. This oil has the ability to keep functioning at the highest level for the longest possible time. Synthetic Oil gives your engine better viscosity temperature response, better low temperature fluidity, better thermal stability better oxidation stability, lower volatility, better deposit control, and better wear control. This in return reduces risk of equipment failure, promotes trouble free operation, reduces maintenance costs, extends service life, and long term engine durability.

This oil for small engines is proven to meet the demands of 4-cycle engines.



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This oil could be a little more expensive, but there are reasons for the price. This is a specialty from Cummins. This engine oil is specially manufactured to provide maximum protection with minimum oil consumption. This is a good product it is also considered an OEM part.

This oil does a great job at lowering friction in your generators engine to ensure it has a long working life. All Cummins oils are extensively factory tested to make sure they maintain quality engine performance when using them.

The main features of the oil: it is designed for RV Generator Engines; viscosity grade: SAE 30W; formulated to reduce consumption and engine wear due to high temperature due to oil oxidation and viscosity increase.

5. Pro Honda GN4 Oil 10W-30

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Generator oil type

The name Honda itself means the state of art technologies together with high quality and high precision. The above is also true of this oil. Honda selected the highest-quality base stocks and developed an additive package specifically designed for the unique requirements of gas generator engines. GN4 has better shear-resistance, viscosity stability and cleanliness to meet the requirements and stresses of a new era of engine technology. The oil is known to lubricate engines working parts faster than most motor oils. They also make excellent cold weather oils if you are going to be using your generator during the colder winter months.

Thought about controlling engine oil

The best practise is to change the engine oil once a year in all the machines with small engines you have around your house (chain saw, lawn mower, generator and so on). The best time to change the oil is before a big amount of seasonable tasks for the machine. The most obvious example for is a spring for a lawn mower. If you, not the oil is contaminated with water of debris, it makes sense to check the sources of this dirt and to change the oil. Always make sure the oil level in each gas powered item you own is always at the recommended fill level too.

Best oil for electric generators

It usually makes sense to change not only engine oil, but also change the gas filter and change the spark plug. This won’t cost much and in most cases you will note a better running of the engine.

Best oil for natural gas generators

All the engine oils are different, prior to pouring the oil in your generator read the properties and the recommendations both of the generator and of the oil manufacturer. It is very important for a small engine to run with the correct oil, which will ensure the best lubrication, temperature control, and prevent depositing inside of the engine.

Best Oil for Portable Generator

If you’re looking for a back-up power source, the best option is a generator. They come in all sizes – with some big enough to power your home five times over. For most people, the smart option is to choose a portable generator. They combine an ample power source with convenience and mobility. Portable generators are also great for camping and RV enthusiasts. Above all, they’re a great tool to have in case of emergency.

Oil for power generator – what engine oil should I use?

There are many differences in engine oils, but which is the best generator oil? How do the types of engine oil differ and what should you consider when buying oil for generators? This is the purpose of the following guide.

For information in advance: This guide applies to most mobile modern emergency generators with 4-stroke gasoline or diesel engine. Most statements can therefore also be transferred to other power generators, but the respective manufacturer’s data and specifications should always be observed and adhered to.

Things to know about power generator oil

Monograde oil vs. multigrade oil – What are the differences between engine oils?

The biggest difference between monograde oil and multigrade oil is the fluidity of the oil. In a monograde oil, the fluidity is fixed, so different oils are then needed for different ranges and temperatures. In a multigrade oil, additive additions such as polymers improve the lubricity at low temperatures and at the same time it can be used at higher outside or engine temperatures.

Multigrade oils can be used in winter as well as in summer and this is the most important difference. Since a power generator needs to be operational at all times, winter as well as summer, a multigrade oil is the best choice as a power generator oil.

The viscosity of engine oils

Manufacturers’ viscosity classifications are given according to SAE of the Society of Automotive Engineers. This is an institute that sets the standards for oils.

The most common classification looks something like this: SAE AW B or SAE 10W 40.

The first value of this classification can be between 0 and 25 and indicates the low temperature viscosity. It indicates with this value how fluid the engine oil is at low temperatures.

With the second value, the number can be between 20 and 60 and indicates how the oil behaves at high temperatures and how viscous or fluid it is.

Overall, the lower the numbers, the lower the viscosity. This means that the engine will run more smoothly, but will not be able to handle as high a load.

As an example, SAE 5W 50 engine oil is more fluid at cold temperatures, but more viscous at high temperatures than an SAE 10W 40 engine oil.

The types of engine oil

When buying power generator oil, you can choose from the following options:

  1. mineral oils
  2. semi-synthetic oils
  3. fully synthetic oils

Mineral oil:

A mineral oil is produced by is produced by refining petroleum. Since it has a certain viscosity, it is only suitable to a limited extent for the operation of modern gasoline engines.

Semi-synthetic oil:

A semi-synthetic oil is made from mineral oil as well as synthetic additives. Compared to mineral oil, it has significantly better lubricating properties, but is more expensive than mineral oil!

The fully synthetic oil:

In the case of a fully synthetic oil, the basic material also consists of mineral oil. However, this is completely disassembled at the molecular level and then reassembled. This process makes the oil much more resilient and thus offers optimum lubricating properties. The fully synthetic oil is the most expensive oil, because the manufacturing costs are very extensive. However, the fully synthetic engine oil thus offers the best lubricating properties and is therefore the optimal oil for power generators. With a mineral or semi-synthetic oil, deposits may occur under certain circumstances.

Some manufacturers, such as Denqbar, therefore recommend only fully synthetic engine oil for the operation of their power generators. As a rule, however, mineral or semi-synthetic engine oil is completely sufficient, unless it is expressly stated in the instructions or manufacturer specifications.
So which oil is the right one for generators?

In Germany and its temperatures, the mineral oil 15W 40 is sufficient for the operation of a power generator. Semi-synthetic engine oil 10W 40 is also suitable. This general-purpose oil is similar in price to the 15W 40.

In warmer areas, at temperatures above 35 degrees, a 10W 50 engine oil should be used, because here the lubricating film cannot tear so quickly.

Basically, a 10W 30 or 10W 40 is recommended as oil for generators. These are also called universal, multi-purpose or all-rounder engine oils. A higher-quality one is always recommended, because you can usually enjoy it longer. Those who are willing to invest a higher price should do so.

If the generator runs only 4 – 5 times a year, then you can also calmly fall back to a cheap generator oil. The manufacturers usually recommend the appropriate and most suitable engine oils for their power generators. Therefore, to be on the safe side, you should always take a quick look at the manual before buying power generator oil, because the important specifications of the manufacturer are written here.

2-stroke and 4-stroke engines – What should I pay attention to?

Depending on the engine, you should buy the engine oils intended for it. The engine oils are marked as 2-stroke or 4-stroke. It is advisable to buy a 2-stroke oil for a 2-stroke engine.

The best oils for generators

Synthetic oil for generators

The lights flicker during the storm, but you don’t even notice it. Finally, you have a generator for the backup.

But when was it last serviced?

You probably run your generator once a quarter and are religious about using fuel additives to stabilize the tank.
There are few tools you will buy in your life that are more practical than a portable gas generator. You are a saviour when the occasional storm turns off the power, and you can also make any camping holiday a much more enjoyable experience. Like any mechanical device, they require regular maintenance and must be kept in good working order. Do you need a new pipe wrench clone?

But what about the oil?

Whether you use a dedicated home standby generator or have portable generators that you want to use (my personal system), you want to invest in oil that can withstand the endless months of sitting and still protect the engine instantly the moment you need it.

If the backup power is needed, it is also likely that your generator engine will run continuously for several days. Is it ready for the job?

According to toolspost expert team, Shell Rotella T6 Full Synthetic Oil is the best oil for generators.

It is often overlooked that the most important moving part of any engine is its oil. Engines do not function without oil. When it comes to generators, it might be absolutely necessary to have the right oil and maintain it properly.

Generators are by definition important equipment; if you need one to pump heat, light and water, you really want to make sure your oil is up to date. Different types of engines require different types of oil, and generators are special machines. If they are used with the right oil, they should never let you down.

Do you need a new oil for your generator but have no idea how to choose it? Then take a detailed look at our Buyer’s Guide. In addition to the tips and features you should be looking for, you will also learn more about the best and most reliable oil brands we recommend.

Quick Tips to Buy the Best Oil for Generators


As always, the first step in our Buying Guide is to take a look at the user manual or instruction manual you received with your generator. You will find any information you will ever need inside, so do not throw it away.

From your own experience, you will usually find information about the engine oil you need in the Maintenance section of your manual.


The most important feature to consider when selecting the engine oil for your generator is its viscosity. As mentioned above, you will find the recommended type in the Owner´s Guide or Manual.
In most cases you will need a SAE 10W-30.

The SAE refers to the rating system developed by the Society of Automotive Engineers. The rest of the code refers to the viscosity oil´s at different temperatures.

The first number in the code, in this case 10W, means how well this oil can be extracted at cold temperatures. The W refers to the word winter (not the weight). The second number in the code indicates how well the oil can be pumped when heated to 212 degrees Fahrenheit (100 degrees Celsius) or higher.

In addition, you should choose a high quality detergent oil with the service classifications SJ, SL, SM or SN of the American Petroleum Institute (API).

However, always check the correct type of oil in your instruction manual and do not rely solely on our recommendations. It may vary from one generator type to another. Filling in an oil other than the recommended one may cause premature wear of individual engine parts.


Another thing to consider when choosing the best oil for your generator is the temperature of the environment you will be using it. In fact, this has been highlighted in every single user manual we have seen.

If you will be using your generator in a very cold environment that only allows very low starting temperatures, a 5W-30 may be a better option for you. However, you must be aware that this oil is associated with increased engine oil consumption at higher operating temperatures, so check its level before each use.


Another thing you should consider before deciding what oil is good for your generator is to know what type of engine it is using. In our experience, there are only a small number of generators with a 2-stroke engine and a large majority of generators with a 4-stroke engine.

Each type requires a different type of engine oil.

While in a 4-stroke engine you use oil and fuel separately, in a 2-stroke engine you can either mix fuel and engine oil in a recommended ratio yourself or you can buy a premixed solution.


Finally yet importantly, you should never try to save engine oil for your generator. Favoring a lower price over a high quality product can lead to major concerns later on.

Rather, you should invest a little more in reliable brands, such as:

  • Honda
  • Onan
  • Briggs & Stratton
  • Mussel Rotella
  • Engine 1
  • Generic
  • Craftsman

The purchase of the right generator oil is crucial for the functioning of your engine. As we have seen, the generator manufacturers themselves produce oils that give their own products the best performance and longest life.

While these are some of the biggest names in the generator market, engine oil sold for use in these and other engines of similar size and speed may be derived from brand names more commonly associated with the automotive industry.

It is worth being careful. Choosing the wrong oil could be expensive and cost you more than money.

Here are some things to consider when choosing the engine oil for your generator:

Do you know your generator?

There is a wide range of power generators on the market, which makes the choice of oil more difficult than before. Largely, portable generators have been manufactured by certain companies to work with fairly normal oils;

Therefore, if yours breaks down at a campsite, you can probably borrow some from another friendly camper.
Today, generators are more readily available in manufacturing forms that require specific maintenance, including generator oil. Manufacturers will always recommend their own brand of engine oil;

However, it is still the case that other brands can function well. While the choice is greater, you can find a brand of oil on the market that actually has a better value.

Many people who rely on generators have the same for years and years. Reliability is by far the most important factor in usage.

This applies to the oil that keeps them running; and as the saying goes, if it is not broken, do not fix it. In today’s market this may not be such good advice. Do some research.

Real or synthetic?

This is a question that is often rightly asked when it comes to oil for generators. While the users of other engines may not have a choice for different applications, the increasing demand for synthetic lubricating oil often comes from the users of such small engines.

The main reason for this is the temperature these engines reach. Two-stroke engines rely on high temperatures to work efficiently, and traditionally generators have used them.

As we have seen in some of our reviews, synthetic engine oil is highly recommended for use in these engines, as it does not suffer from the problem of increased viscosity.

Synthetic oil is otherwise a consistent product; its price does not depend on that of a barrel of crude oil. Although it can be more expensive to bottle, its properties mean that it lasts longer than conventional engine oil. In the long run, this can save you money.

Of course, more oil that is powerful means a more powerful generator. This means less fuel, which is a consideration. Over time, synthetic oil will maintain your engine very well. Besides avoiding stalls and traffic jams, this can mean that you never have to buy a new generator.

It may not be at the top of the list, but there are also environmental aspects to burning fossil fuels. Apart from everything else, it will run out one day.

Can you use synthetic oil in a generator?

The short answer to this question is yes and is sometimes recommended. To understand why you first need to understand the differences between synthetic and conventional. Both types of oil initially come from the same place – the soil.

Synthetic differs in the higher process of refinement and distillation, where more chemicals are added to modify and improve the oils.

This process produces a cleaner oil that provides a much higher level of protection while at the same time providing higher performance, especially for smaller engines. This has to do with the overall higher viscosity at extreme temperatures – synthetic oils lubricate better in cold conditions or under high loads associated with high temperatures and dust.

The main disadvantage of using synthetic small engine oils is that they are hard on the handbag. But for reliable backup performance and durability, these plastics are unbeatable.

In addition, the maintenance schedule of your generator can be extended, resulting in less downtime for power tool repairs.

How often should I change the generator oil?

Generator oil filters and oil filters should be changed every 100 hours of generator life. With synthetic oil this time can be doubled to 200 hours.

In the event of a longer power failure, i.e. approximately every eight days. By comparison, most lawnmowers recommend changing the oil once every 50 hours. If in doubt, remember that an engine has never been worn out by too many oil changes. As a side note, most lawn mower manufacturers recommend changing the oil filter and air filter once every two oil changes.


Q: What are the different groups of base oils or synthetic oils?

Synthetic oils fall into different categories from Group 1 to Group 5, which differ in their performance, although you can expect Groups 5 and 4 to provide the best performance. The rest of the groups then follow, with Group 1 being the lowest, followed by Group 2, then Group 3.

Q: How much oil should I expect my generator to consume?

Basically, there is nothing like a standard amount of oil that you should expect generators to consume. The reason for this is the number of variables that affect the amount of oil you should expect a generator to consume. These variables include the model, engine hours, load and other factors. It is therefore up to you to check your oil tank to ensure that the generator is in good condition.

Q: What type of generator oil is suitable for my engine?

Different engine types require different types of generator oils, with 7kW, 12kW and 15kW air-cooled generators requiring 10W-30 for temperatures above 20°F and 5W-20 or 5W-30 for temperatures below 20°F. However, you can use 5W-30 synthetic oil all year round after the first oil change.

On the other hand, liquid-cooled units require 15W-40 oil. You should ensure that this oil is SAE compliant and meets the requirements of API service class SF for gasoline engines. One point to note is that if you have an engine that has been previously serviced with conventional oil, then you should top it up with the same type and avoid mixing it with synthetic oils as this can damage the engine.

Q: What happens if I put too much or too little oil in my generator?

If you add too much oil, the resistance of the engine may increase and even cause the oil to leak from the air filter. On the other hand, too little oil is consumed quickly, which activates the oil warning system to prevent the engine from burning. Therefore, it is important that you fill in the correct amount of oil based on the instruction manual.

Q: Should I top up or replace the oil in my generator?

While you can choose to top up your engine, it is best to change the oil so that you can extend the life of the engine. The reason for this is that the oil deteriorates over time due to high engine temperatures, resulting in a reduction in efficiency. So choose replacement, not refilling.

Concluding remarks

As the technology advances, we will have more choices. This applies to generator oil as well as everything else mechanical. Just to drive the point home, engine oil is a part of your engine.

As technology advances, synthetic oils become cheaper and can compete better with the old type.

For such a cheap product, it is worth thinking about what you are actually buying. For many people, engine oil is an afterthought; think about fuel, etc., until their generator stops working.

Don’t be fooled by the fact that all oils are the same. There is a reason why they have our recommendations for the best oils for generators. They are all made to high standards, and that’s because they really know which products are healthy for small engines. When you buy oil for your generator, you can’t do anything wrong by using one of the oils tested here.

We hope that our guide to the best generator oils will help you make the right choice.

David Muench (Carnes Mechanical)

David Muench (Carnes Mechanical)

Hey, I’m David. I’ve worked in a cars store for 6 years. I write reviews and guides, helping people to choose the most suitable technicals and best product for them. I’m happy to finally share my knowledge of the industry here, on CarnesMechanical.

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