How to change/replace generator oil

How to Change Oil in Generator-Step by Step

The engine oil in your generator plays important roles in lubricating the engine and cooling it as well. After the first 5 break-in hours or running the engine, you should change the engine oil immediately before you start using it to power the house.

This particular change of oil and any other subsequent ones are quite easy to handle given that they can be carried out in a few steps. Before changing the oil in your generator, you should know the type of oil used, the oil filter type, the amount of oil required, and the rate at which the oil should be replaced.

If, during the oil change process you run into a problem whose solution you’re not sure of, always check the generator’s manual or call in an expert if that too doesn’t work. Keep in mind that it’s much easier to avert a problem than buy a new part or, in the worst case, buy a whole new generator.

Changing Generator Oil: The Steps

You need the following items for this process:

  • Correct oil type
  • Correct oil filter type
  • Clean towel and brush
  • Oil funnel
  • Oil filter wrench and ratchet
  • Drain oil can
  • Protective gloves
  • Protective goggles
  • Correct socket wrench size
  • Phillips and flat screwdriver

Some items such as the oil funnel may come with the generator and thus aren’t necessarily bought on their own.

The procedure is as follows:

Protect yourself

While this process is usually safe and mostly clean, it’s always wise to take care of yourself by putting on protective gear. You should have your gloves and googles on throughout this process to stay safe.

Warm the engine oil

Cold and old engine oil tends to be sticky and, given that it’ll have some sediments in it, these will settle to the bottom of the engine. To ensure you drain away all the oil and the dirt it contains, you should warm up the engine for about 10 minutes. You do this by running the engine at about 50% load for 10 minutes then you turn it off.

Oil for Generator
Generator Oil

Place the generator on blocks

To be able to drain the oil from the generator, you need to place the generator on a platform with spaces in between them for the drain oil can. The two blocks should be placed such that the generator rests on them to allow space underneath it.

Some generators can be quite heavy and will need more than one person to lift and place on the blocks. Make sure the generator is turned off before placing it on the blocks. Also, while on the blocks, don’t run the engine as the vibrations will topple the generator leading to damage.

Remove the spark wire

You then need to remove the spark plug wire to avoid turning on the generator by mistake while you’re changing the oil. If the generator turns on while you’re draining the oil, it’ll likely get damaged due to the lack of a lubricant. Besides that, the generator will be on blocks and the vibrations will likely topple it over.

Identify the spark plug wire from your manual. If you have experience with generators, you already know where it is. Some large generators can have more than one spark plug hence you need to identify all of them for this stage to be effective.

Hold unto the spark wire then, while pulling it out, gently swing it from side to side (clockwise and counter-clockwise) until it comes off. Do the same for any other spark wires (if the generator has more than one spark plug).

Prepare to drain the oil

Next, you need to locate the oil drain plug in readiness for draining the oil. The drain plug and drain hole are located on the low side of the generator engine block. The plug is usually a 3/8” nut with a square or hexagonal head.

You should also get a container into which you will drain the oil. This can be any container that doesn’t leak and is large enough to take all the oil from the engine. You can easily tell the amount by checking the amount of oil the engine can take.

You should also remove the oil dipstick.

Drain the engine oil

The engine oil can be easily drained once you remove the drain plug. Simply use a ratchet and 3/8″ socket to loosen the plug. You then twist the rest of it out in the counter-clockwise direction by hand. Make sure you have placed the container in the right position to receive the oil from the drain hole. Remove the oil fill cap to allow the complete draining of the engine oil.

Don’t pour the oil into water or a land area but in the right location. Oil is a pollutant that can kill aquatic life hence should be disposed of correctly. Taking it to a recycle center or spare parts store is much better than trying to get rid of it on your own.

Change the oil filter

Each time you change the engine oil, it’s wise to also change the oil filter. This is because you won’t get any benefit from using new engine oil with an old oil filter as the dirt from the oil engine oil will easily find its way into the new oil thus rendering it less effective.

To change the oil filter, make sure you get a new one that’s exactly similar to the one you have on your generator. Use a wrench to loosen up the current oil filter then twist off the rest of it by hand. You should know that the oil filter can be quite hot after running the engine hence the need for gloves. Also, ensure you have a container directly under the filter to capture the old engine oil as it drains out.

Check the oil filter adaptors and gaskets for any debris then clean it out as needed.

Screw on the new oil filter then tighten the last few turns with the wrench to ensure it’s tightly held in place.

Add the new engine oil

Remember the oil drain plug? You need to wipe it clean then reinstall it to the drain hole. You should tighten it with the socket ratchet then proceed to pour the new engine oil into the engine. Use the funnel to pour as much engine oil into the engine. Ensure it’s the right type of oil for this purpose.

Recommended Reading: How much Oil does a generator take?

Reconnect the spark plug wire

Reattach the spark plug wire onto the protruding end of the spark plug. Push the end of the spark plug wire until you hear or feel a clicking sound. Reattach any covers you might have removed from the generator to complete the process. Return the dipstick as well.

Run the engine

Turn on the generator then let it run for about 10 minutes before turning it off. This allows the new oil to run through the engine. After shutting it down, wait for a few minutes then check the engine oil level with the dipstick. If it’s right (just below the MAX or FULL level), then you’re good to go. If less than that, top it up to the required level.


Generator oil change hours

It takes between an hour and two to change the engine oil for most generators.

How often should I change the oil in my generator?

You should change the engine oil in your generator every 100 hours.

What will determine how often to change?

The frequency of oil change depends on how often you use the generator and how long it runs each time it’s used.

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