What Kind of Oil Does a Generator Use?

Oil is a vital part of the generator engine’s operation.  The internal combustion operation requires oil to lubricate the engine’s components by reducing friction.  The oil’s job is to create a barrier between the moving parts to prevent contact that can cause damage.  Oil cleans components as it removes particles that can build up inside the engine.  It keeps the engine’s parts from becoming corroded.  It is also responsible for keeping the engine cool by allowing parts to move efficiently. But what kind of oil does a generator use, and more importantly what kind should it use?

Checking the oil in your generator and changing it every 100 to 150 hours of operation are as important as regularly changing the oil in your vehicle.  Doing so extends the life of your generator engine.  When not using your generator regularly, be sure to start it and allow it to run for 10-15 minutes at least once a month.  This allows the oil to keep the parts lubricated and clean while sitting idle.

Before you send your spouse to the store to buy oil for your generator, you should read the owner’s manual to find out what type of oil is recommended for your unit.  But, in case you need some additional guidance, here are a few pointers.

You will note that many oil containers will state, “SAE” which is the classification of the oil and stands for the Society of Automotive Engineers.  It was officially established in 1916 to provide the engineering standards for the automotive industry.  This includes oil and gasoline standards that are in use across the world today.

Oils are rated by their viscosity.  Viscosity is the thickness of the oil.  The thinner the oil, the more fluid it will be in colder weather and the easier it moves when starting your engine.  Heavier weight oil is needed in warm weather to protect the engine components.

Determining which oil is best for your generator engine will depend on a couple factors.  One is the viscosity – or how fluid the oil is when exposed to friction.  The lower the first number, the thinner the oil which is good for colder conditions.  The “W” stands for winter. The number following the “W” in the description defines the thickness of the oil when the engine is running at a normal operating temperature.

What Kind of Oil Does Generator Use

The other factor is outside temperature.  As stated, cold weather operation requires a thinner oil.  The hotter the weather, the thicker the oil needs to be for effective and efficient component operation in the engine.

There are different types of oil, as well.  Single grade, multigrade oils, and synthetic oils can be found on store shelves easily. 

Single grade, or monograde, oils are based on the viscosity grade, such as SAE 30 or SAE 40.  Outdoor temperatures and the use of your generator will determine which grade of oil you will need for efficient operation.  Engine makers design them to run at certain viscosity ratings.  Therefore, it is important to use oil as recommended by your generator user’s manual. 

A multigrade oil is typically one that has an additive known as a Viscosity Index Improver.  A multigrade oil changes its fluidity by temperature. The additive begins to work when the weather warms and the fluidity of the oil needs to be heavier.  Examples of a multigrade oil are 5W-30, 10W-30, etc.

Synthetic oil is made from artificial chemical compounds with distilled crude oil as a base.  One of its features is that it contains less contaminants than either single or multigrade oils.  This prevents sludge and other contaminant build-up within the engine.  A synthetic oil will cost more but is designed to last longer than a single or multigrade oil. 

If you want your generator to last through several years of operation, there are some important maintenance features to consider.  Monitor the number of hours of operation so you can change the oil as recommended.  Most generators need to have the oil changed between 100 and 150 hours of operation.  This is important when using a single or multigrade oil.  By their nature, these oils contain micro-contaminants that degrade the oil through use.  As the oil cleans particles and other debris from the components, these build up, and need to be replaced with clean oil to protect the engine.

There are 11 viscosity grades used in the US, ranging from 0W to 30W.  These are often referred as the weight of the oil.  The most used are shown below.

SAE Classification Temperature (Fahrenheit)
 Temperature range that the oil functions (lubricates) optimally
SAE 5W-20-37⁰ to 77⁰
SAE 5W-30-22⁰ to 86⁰
SAE 10W-30-20⁰ to 96⁰
SAE 10W-40-15⁰ to 100⁰
SAE 15W-30-13⁰ to 95⁰

FAQ

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What is the best oil to use in a generator?

Look for oil brands that meet the SAE (Society of Automotive Engineers) standards. 

Therefore, the important feature should be

1) The oil weight recommended by your generator owner’s manual, and
2) The outside temperature. 

The colder the weather, the smaller the number on the oil should be (i.e., 5W-30 indicates temperatures falling between -22⁰ to 86⁰ Fahrenheit). If running your generator is a hotter climate, you should consider a heavier weight oil, such as a 10W-30 or 10W-40.

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What oil do you use in a petrol (gasoline) generator?

Always check the owner’s manual for the recommended oil to use in your generator engine.  A gasoline engine is an internal combustion engine that requires oil to lubricate, cool, and clean the working parts.  Outside temperature affects the way the oil can work.  It is based on the viscosity rate, or how fluid the oil is at varying temperatures.  The numbers on the oil indicate how well the oil will work in varying temperatures.  A 10W-30 rated oil works best in temperatures ranging from -20⁰ to 96⁰, for example.

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Can I use 5w30 oil in my generator?

If you are in a colder climate, then using a 5W-30 rated oil is acceptable.  This oil works best at colder temperatures.  However, if you are running your generator is warmer temperatures, a 10W or 15W rated weight would be better.  The lower the first number is, the more fluid the oil and, therefore, easier on the engine for cold starts. 

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Can I use SAE 30 instead of 10w30 in my generator?

An SAE 30 oil is also known as a single or monograde oil.  Generally, these are used in seasonal engines, such as lawn mowers.  The 30 number relates to the thickness (viscosity) of the oil when the engine is running at a normal operating temperature.  Refer to your generator owner’s manual for recommendations on the oil grade that is best.

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When should I change my generator oil?

Manufacturer recommendations for how often to change your generator oil are listed in the owner’s manual.  Generally, the recommendations are between 100 and 150 hours of use.  It is important to follow those recommendations so sludge or other buildup within the engine are released.  Dirty oil can cause damage to the engine as it degrades and reduces its ability to lubricate.

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Can I use synthetic oil in my generator?

Always refer to the recommendations in your owner’s manual, but in general, the answer is yes.  Synthetic oils are thinner and through their manmade chemical enhancements are designed to benefit engines.  It is important to note that if synthetic oil is recommended for use in your generator, you should not use single or multigrade oil, as these can cause damage over time.

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What is the best oil to use in a generator?

Look for oil brands that meet the SAE (Society of Automotive Engineers) standards.  Therefore, the important feature should be 1) the oil weight recommended by your generator owner’s manual, and 2) the outside temperature.  The colder the weather, the smaller the number on the oil should be (i.e., 5W-30 indicates temperatures falling between -22⁰ to 86⁰ Fahrenheit). If running your generator is a hotter climate, you should consider a heavier weight oil, such as a 10W-30 or 10W-40.

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What oil do you use in a petrol (gasoline) generator?

Always check the owner’s manual for the recommended oil to use in your generator engine.  A gasoline engine is an internal combustion engine that requires oil to lubricate, cool, and clean the working parts.  Outside temperature affects the way the oil can work.  It is based on the viscosity rate, or how fluid the oil is at varying temperatures.  The numbers on the oil indicate how well the oil will work in varying temperatures.  A 10W-30 rated oil works best in temperatures ranging from -20⁰ to 96⁰, for example.

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Can I use 5w30 oil in my generator?

If you are in a colder climate, then using a 5W-30 rated oil is acceptable.  This oil works best at colder temperatures.  However, if you are running your generator is warmer temperatures, a 10W or 15W rated weight would be better.  The lower the first number is, the more fluid the oil and, therefore, easier on the engine for cold starts. 

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Can I use SAE 30 instead of 10w30 in my generator?

An SAE 30 oil is also known as a single or monograde oil.  Generally, these are used in seasonal engines, such as lawn mowers.  The 30 number relates to the thickness (viscosity) of the oil when the engine is running at a normal operating temperature.  Refer to your generator owner’s manual for recommendations on the oil grade that is best.

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When should I change my generator oil?

Manufacturer recommendations for how often to change your generator oil are listed in the owner’s manual.  Generally, the recommendations are between 100 and 150 hours of use.  It is important to follow those recommendations so sludge or other buildup within the engine are released.  Dirty oil can cause damage to the engine as it degrades and reduces its ability to lubricate.

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Can I use synthetic oil in my generator?

Always refer to the recommendations in your owner’s manual, but in general, the answer is yes.  Synthetic oils are thinner and through their manmade chemical enhancements are designed to benefit engines.  It is important to note that if synthetic oil is recommended for use in your generator, you should not use single or multigrade oil, as these can cause damage over time.

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