How To Change The Oil in the Generator Using Different Methods

Generators always come in handy when we need power for outdoor activity, be it Jobsite work involving electric equipment or providing electricity at home or an outdoor event. Click here if you want to know more about generators.

Therefore, it is always good that we get familiar with the working and maintenance of a generator. Some of the maintenance activities include changing generator oil, changing the oil filter and changing the spark plug. Today we will be looking at changing generator oil. 

If we learn how to change the oil, it can eventually save a lot of money involved in the repair and maintenance cost. It can also help improve the performance and longevity of the motor and reduce the toll it takes from regular usage.

So, if you own a generator or planning to buy one, then go ahead with this article because today we will explain how easily one can replace generator oil without any hassle or much expense. This guide will be separated into two parts, one part involving the small-sized portable generators and the other part involving the frame-mounted generators.

How does a generator work?

A generator works the same way a typical motorbike or car engine works, with the only difference being that IC engines involved in car engines produce mechanical energy but in the case of generators that mechanical energy is further processed to convert it into electrical energy.

Most portable generators use diesel or natural gas as fuels. The fuel is combusted which creates an explosion in the chamber in order to move the piston periodically, and this piston is connected through a shaft to produce mechanical energy. If you want to know more about a motor’s mechanism click here

WEN Generator Starting

This mechanical energy is then used to produce Alternating Current (AC) using an AC generator. 

Generator oil is added to the engine for lubrication of the system so that it does not suffer too much wear and tear and runs smoothly. At the same time, it also ensures that the metal parts do not get corroded by exposure to water or humidity. These oils are composed of petroleum-based Hydrocarbons, polyalphaolefins (PAO) and some percent of ester. The oil composition may vary based on its use. 

If the engine is of a smaller scale, then single viscosity oils can be used as lubrication and if the engine is of larger size and involves stronger fuels, the viscosity of engine oil can also be higher. 

Oil can also differ based on the number of strokes it takes per cycle. Generally given as a 2-stroke or 4-stroke engine. Portable and small-scale generators are usually 2-stroke ones and engine oils are added in the ratio of 1:25 – 1:50 with respect to the volume of combustion fuel used and are mixed with it.

Click here to learn more about Motor lubrication oils.

Over time, this oil starts to collect dirt and waste making it unusable later. Modern generators tend to have indicators to notify the user if the oil can be damage-causing to the engine. Our next section discusses how frequently we should change the oil.

How frequently should you change the generator oil?

If the generator you own is a newly bought one, then it is good if you change the oil within 2 months’ usage period. However, if the generator has been with you for more duration it is good to get it changed in 5-6 months’ time or 80-100 hrs. of usage. Any use beyond this period can end up harming your generator leading to bigger issues. 

It is good to get it changed even if you have not used it much because it gets exposed to moisture if not used regularly. 

Tools and equipment required when changing oil:

Tools and equipment

1. Screwdriver

A screwdriver might be needed to remove the maintenance panel and open the drain panel. 

Frame-mounted generators do not have a maintenance panel so they might not require a screwdriver, but those looking for small-sized generators should keep a screwdriver with them for opening the panel. In case you do not own a screwdriver, you can buy the one in the link given below

2. Spanner or wrench

wrench for opening oil cap

A wrench or a set of spanners might be needed to remove the drain plug. In case you do not own a spanner or a wrench, you can buy the one in the link given below. 

3. Funnel

We will use a funnel to collect the drained oil and fill the fresh one. It is always good to collect the used oil and get it recycled. A funnel can be easily found at home, but in case you do not have one you can cut out the opening of a smaller sized bottle to make a funnel.

4. Gloves, protective goggles, and towel or cleaning cloth

This is to make sure that we do not get in direct contact with the hot fluid. We might also need a machine or a second helper to lift the generator to a height if the drain plug is at the bottom side of the machine. Use bricks or blocks to level the generator. In case you do not own gloves and protective goggles, links are provided below.

If you own a Honda portable generator, you can check the link below to buy any of the oils and chemicals. Make sure that you check the power rate and viscosity compatibility of the oil you buy with your generator. A false product can end up harming your machine.

Steps to change oil: 

For Frame-mounted generators

Champion 3800-watt Dual Fuel Generator

The image shown is a Clarke CP5050N 5.0kVA. It is a frame-mounted generator that can produce both 110V and 230V voltages. It is powered by a 4-stroke 6HP Honda engine with a 6L fuel capacity.

  • We must start the engine for a few minutes. This step is to make sure that the engine is heated. A heated-up engine will heat up the generator oil, this decreases the viscosity of the oil, making it easier to flow and remove.
  • Turn off the engine after some time and put the generator on a high surface using bricks or blocks if the drain plug is at the bottom.
  • Put on gloves and other safety equipment and turn off the fuel valve
  • Place a bottle or a can (1 liter or above suggested) and funnel its mouth. We are using the funnel to ensure that the least amount of oil is wasted. This is because the oil taken out can be recycled and reused after processing.
Place a Can under Frame-mounted generators
  • Disconnect the spark plug if possible. If you are not sure about the spark plug you can refer to the user’s manual to look for the spark plug.
  • Using a wrench or spanner, carefully open the drain plug while the bottle/can is right next to the plug.
open the drain plug Using wrench
  • In case we want to clean or replace the oil filters, we must gently remove the filters while unscrewing it and place it back to its position carefully without damaging the filter.
Old oil drain
  • Close the drain plug.
Close the drain plug
  • Open the oil fill cap and fill in the new oil.
new oil
  • Now we need to check if the oil is filled up to the top. Usually, people use their fingers to check but it is not recommended. Instead, use a stick to see how much wet it gets when inserting it into the opening.
Oil fill up on Frame-mounted generators
  • Clean off any excess oil spilled into the system using the cloth.
  • Close the oil fill cap and reconnect the spark plug if you disconnected it previously.
  • Turn on the fuel valve.
  • As the last step, turn on the generator and let it run for a few minutes to ensure its proper working condition.

For Small-sized portable generator

The image shown is of a Honda EU1000i. It is one of the more commonly used portable generators with a power rate of 1000 Watt with a fuel capacity of 0.6 gallons. Thus, it provides a decent amount of power with alright runtime.

  • This procedure is like the previous one with a few differences.
  • We need to turn on the engine and let it run for a few minutes.
start your portable generator
  • Turn off the fuel valve and place a bottle or can near the generator.
  • Unscrew the maintenance panel/ access panel using the screwdriver.
Honda EU7000 access panel
  • This Honda EU7000 maintenance panel has been opened using a screwdriver. After opening the panel, it will look something like the above image depending on the model you are using.
  • Put on the safety equipment and disconnect the spark plug if possible. A spark plug might not be accessible in all the models.
  • Open the oil fill cap and tilt the generator so that the oil can pour out into the bottle.
Pour oil in can
  • As we can see in the above image, the oil fill cap is removed, and it is accessible for removal and addition of generator oil.
Old oil Storage
  • Once done, we can pour in the new oil.
  • Now we need to check if the oil is filled up to the top. Usually, people use their fingers to check but it is not recommended. Instead use a stick to see how much wet it gets when inserting it into the opening.
New Oil Filling up
  • Clean off any excess oil spilled into the system using the cloth and put back the maintenance panel.
  • Close the oil fill cap and reconnect the spark plug if you disconnect it previously.
  • Turn on the fuel valve.
  • As the last step, turn on the generator and let it run for a few minutes to ensure its proper working condition.


  • Turn off the fuel valve before opening any plugs to ensure that there are not any leakage or fire hazards
  • Safety gloves are necessary when doing this work because we will be keeping the generator warm
  • Remove the spark plug, not removing plug can lead to accidental startup of the engine which is of course dangerous
  • Keep the bottle and funnel steady to minimize the loss of removed oil. The bottle should be made of hard plastic or else the hot fluid might melt the bottle from its heat. The removed oil can later be recycled and used again after remanufacture.
  • Handle the generator carefully when tilting, get a second person to help you with this task.
  • Go through the user’s manual in case of doubt regarding parts of the system.
  • Buy the replacement oil from a reliable source and make sure that the oil that will be added is the appropriate one. Inappropriate oil can end up damaging the engine.

Why should we consider changing the oil?

There are multiple reasons to consider changing oil:

  • Prolonged usage of oil can cause an accumulation of dirt and waste in the engine damaging it even further.
  • Oil, after long use, loses its lubrication properties and causes more issues to the engine.
  • Oil starts to easily be affected by moisture and the system will be easily affected by water.

The oil, after being added to the engine, should be replaced within 5-6 months or around 100 hours of usage. Newly bought generators should be treated with new oil in less than 2 months.

If the generator is not used frequently, the oil needs to be replaced more often because the engine is not suffering enough motion for the oil to move and lubricate and treat the surface of the engine. Therefore, it is suggested to keep using the generator often to keep it lubricated.


Be it small a task like lawn mowing, snow blowing, or something like providing electricity at places, generators have always been an independent person’s go-to machine when it comes to portable power sources. It is also used when we suffer from an unexpected power cut and we need to rely on a conventional energy source. 

Diesel and natural gas are some easy to obtain fuel, at least for the next few decades and can provide lots of power compared to a battery-based portable power source. Thus, it is always a reliable source. And thus, it is necessary to maintain the equipment which enables us this power.

We hope that this article helped you understand the working of fuel-based generators better and you got familiar with the maintenance of the device. We also hope that learning from this article will help you in the future when you must service your machine on your own.

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