How Often You Should Change Oil In a Generator

Generators have become an integral device of modern society. We use them to power our lives when the primary power grid fails us. That said, generators also have their limits, and sometimes they require maintenance to ensure that they function when we need them the most. Neglecting to change the oil of your generator in regular intervals is one of the main components that form part of poor maintenance. So, how often should the oil in your generator be changed?

Different types of generators require varying oil change schedules. You should replace the oil in a portable generator every 50 to 100 hours of usage and diesel generators every 250 hours. Standby generators require oil changes after maintenance, heavy usage, and on a regular schedule.

The interval in which you have to change the oil of your generator depends on the type of generator you are operating. Let us take a look at these examples more in-depth in the article below.

How Often You Should Change Oil In a Generator

Generators come in various shapes and sizes. To determine how often you have to change the oil in your generator will depend on multiple factors. To give a comprehensive answer to this question, we must look at a couple of examples and discuss them regarding the question at hand.

Generator TypeWhen to Change the OilNotes
PortableEvery 100 hours of useDepending on usage, may need an oil change more or less often
StandbyAfter repairs, heavy usage, and on a regular scheduleCheck the manufacturers instructs to know when to change the oil
DieselEvery 250 hours of useChange 50 hours after any repair work

Below, we will look at three examples that can demonstrate how often you should change the oil in your generator.

1. Changing the Oil In a Portable Generator

The most common generator used in the United States is a portable generator. Accordingly, we will discuss this example first.

When it comes to changing the oil of your portable generator, the interval in which you do it will depend on various factors. These factors include the manufacturer of the portable generator, the interval in which you use your generator, and the environment.

Some manufacturers recommend changing the oil inside the generator after the first eight hours of the generator’s use, provided that you’re using your portable generator often. You do this to clear away any contaminants from manufacturing or shipping.

Fuel change related to the regular maintenance of the generator is another story. The frequency with which you have to change the generator’s oil can vary from anything between 50 and 200 hours of the generator’s usage.

That said, the 50-200 hour range can change if you use it in dusty environments, and you might have to change the fuel more regularly. The reason for this is because dust can sometimes contaminate the inner workings of your generator and affect the fuel negatively, making it less efficient than it is supposed to be.

Manufacturers such as Hy-Tech recommend that you do an oil change after every 80 hours of generator operation. Other manufacturers and experts indicate that replacing the oil after every 100 hours of generator usage is better, especially if you use the generator often.

Either way, a safe range is probably between 50 and 100 hours, and maybe a little more if you are not using your generator too frequently.

2. Changing the Oil In a Standby Generator

If you do not ensure that your standby generator has enough oil, it can cause your engine to seize up. This means that your operations will, effectively, come to a standstill until you replace your standby generator’s engine. There are several checkpoints at which you will want to replace the oil in your generator to keep the machine in good shape.

Here is when you should generally change the oil on a standby generator:

  • After initial installation
  • After substantial malfunctions
  • After substantial leaks
  • After heavy usage
  • When recommended by the manufacturer

After Initial Installation

Many standby power generators, if not most, are shipped without containing any oil in the generator. To mitigate any harm from this, confirm to see if the generator comes with or without oil. This will determine whether or not you will have to add oil after your standby power generator installation.

Furthermore, your standby power generator will also require an oil change shortly after the generator breaks down. During break-in, there is a high chance of unwanted particles that can enter into the system of the generator (such as debris) and negatively affect the oil stream of the generator. Accordingly, after the break-in, the oil changing can serve as preventative maintenance to avoid problems down the line.

After Substantial Malfunctions

Many problems related to standby power generators failing are a result of a faulty oil system. You can experience power spikes or other interruptions if you have contaminated oil that prohibits the generator’s motor from performing optimally.

Accordingly, if you experience a malfunction of any type, make sure that you test the oil and investigate if it is ‘dirty’ or contaminated (such as being filled with debris). Additionally, inspect the standby power generator’s filter to see if it is filtering the oil correctly.

If you determine that the oil is, in fact, dirty, replace the oil immediately to prevent any further malfunctions.

After Substantial Leaks

If the oil levels within your standby power generator reach levels that make it unsafe for further operation, the generator should automatically shut off. It could be a strong indicator that your standby power generator has a substantial leak if this happens. Accordingly, you should repair the leak as soon as possible.

After repairing the leak, it is essential to change the oil as well. You do this to ensure that no harmful substances or contaminants enter the standby power generator’s system and that they are flushed out before the generator continues to operate.

After Heavy Usage

No matter the reason, you should replace your generator’s oil after heavy periods of usage. This could be increased production requirements, or the national power grid failed more frequently, which forced you to rely on your standby power generator more regularly.

It is crucial to change the oil of your standby power generator after severe usage because it will simply help the engine perform smoothly and operate efficiently.

When Recommended By the Manufacturer

This one might seem the most obvious but, yes, it is important to change the oil of your standby power generator if the manufacturer of your generator recommends that you do so.

Often, oil changes are not seen as essential and get overlooked. As a result, manufacturers have recommended that you change your oil in certain intervals to prevent engine breakdowns due to oil-related reasons.

To ensure that you comply with this, many recommend keeping track of your oil changing schedule and keeping logs of it. Manufacturers also recommend that pushing a standby power generator beyond its designated limits can strain the oil system and be avoided wherever possible.

3. Changing the Oil In a Diesel Generator

Changing the oil of your diesel generator can prolong its useful life significantly. There are various types of diesel manufacturers and different sized diesel generators produced by these manufactures. Still, there are three general instances in which you should replace the oil in it.

  1. It is advisable to replace the oil of your diesel generator after its first 50 hours of operation.
  1. After the initial oil replacement, it is advisable to replace the oil of the diesel generator 50 hours after the generator has been repaired or overhauled.
  1. Lastly, there is an oil replacement cycle. The oil replacement cycle is said to be similar to that of the oil filter. This replacement cycle is said to last 250 hours or a single month.


In conclusion, the interval you have to replace your oil will largely depend on what type of generator you are running.

Portable generators’ oil has to be replaced, for the most part, based on a specific time that lapsed. The same goes for a diesel generator; after the lapse of a certain period, you should replace its oil.

The only ‘tricky’ generator would be your standby power generator. This generator’s oil changing routine does have a time aspect, but, for the most part, the changing of a standby power generator’s oil depends on specific events that trigger it.

Since most Americans use portable generators, the best advice you can give a layperson is that the range is between 50-100 hours.


Hubert Miles

I've been conducting home inspections since 2002. I'm a licensed Home Inspector, Certified Master Inspector (CMI), and an FHA 203k Consultant. I started to help people better understand whole-house and portable generators.

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