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How to Change Oil in Generator: Pro-Backed Guide

how to change oil in generator
Written by Jamie Masterson

Changing old oil in your generator is one of the common maintenance activities that helps keep the machine running smoothly throughout the stormy season. Not only does the new oil make the starting process simpler and more comfortable but it helps lubricate the engine’s critical components. The replacement procedure may seem a time-consuming operation, but anybody can get it done with the right guidance. If you have the official product documentation ready, you’ll be able to find all the details you need.

How to Change Oil in Generator

Before you start replacing the obsolete filter and oil within your generator, you should think about your protection first. As a precaution, make sure you’re wearing safety glasses and gloves. Once you’ve double-checked that everything is in order, follow these steps –

1. Warm up the old oil

Warm up the existing oil in the generator for a few minutes to allow it to drip out quickly and easily. Hot oil seems to have a much higher liquid consistency. To do this, just turn on your generator and let it work for a few minutes. After several minutes, the oil should be warm enough for you to switch off your generator.

2. Place your generator on the blocks

The next move is to gather at least a few similar blocks and position them on a flat surface. It’s preferable to position blocks on a big, stable table so you don’t have to lean over too much. Then you should place the generator on blocks to make room for the oil drain pipe. Be sure that your generator is correctly positioned, stable, and won’t slip off from your blocks.

3. Detach the spark wire

Once you’ve comfortably seated your generator on solid blocks, find the sparkline and unplug it. This will stop any unwanted start of a generator that is empty of gasoline. While the spark plug is usually easy to find, some models and versions cover this vital component of the generator under plastic covers.

When you’ve figured out where your sparkline is, you’ll need to unplug the wire that’s attached to it. To do so securely, take the spark wire tightly and turn it in any direction while pulling it off at the same moment. This way, even if the spark wire is partially corroded, you can quickly break it loose.

4. Get Ready to dump the old oil

After you’ve detached the spark wire and placed it somewhere secured, you’ll need to find the oil drain pipe. It’s usually a nut with a hexagonal or square head. Since the size and type of this nut vary depending on the manufacturer and version of your generator, reading the user manual is the best way to find it.

If the drain pipe and the parts surrounding it are dusty, take your time cleaning away some oil buildup and stains so you can see what’s going on. Don’t forget to put an oil tray or an empty container under your generator’s drain pipe to collect the last drop of obsolete oil.

5. Remove the oil pipe

After positioning the drain plate to catch any oil spilling from the generator, the next step is to remove the oil drain pipe. Most of the time, a 3/8” socket as well as a ratchet would be needed. The ratchet’s primary function is to remove the pipe. After that, unscrew the existing threading carefully after removing the socket and ratchet. However, bear in mind that as soon as you pull the pipe, the oil will begin to leak out of the generator. Make an effort to collect every last drop of oil in the drainage pan. This material should not be thrown away because it can quickly pollute soil and water.

6. Remove the old oil filter and replace it with a new one

You should also replace the oil filter if your generator has one. Replacing both the filter and the oil at the same time will help your generator last longer and avoid engine failure. To replace the oil filter, you’ll require a high-quality wrench. Remove the wrench once the screws are loose and finish the job by hand. Always use protective gloves when working with an oil filter because it can be very hot.

Often, plenty of the old oil can leak out of the hole or even the filter itself, so make sure you have a drainage pan underneath your filter. Check for dirt or gasket substance on the closing surface of the oil filter connector and clean it if appropriate. After that, take the new filter and gently lubricate the gasket with regular motor oil. Begin by carefully screwing it in before the gasket comes into contact with the filter connector. Be sure not to overtighten the filter or it will get damaged.

7. Tighten the pipe and add new oil

Once you’ve installed the new filter, you’ll need to replace the oil drain pipe. Manually screw it in and after that tighten it with your socket wrench. After that, detach the oil fill cover and replace it with a funnel. Now slowly pour the fresh oil into the generator. Since different manufacturers and generator versions need different types of oil and volumes, consult the official user manual to figure out how much oil you’ll need. After adding the specified quantity of oil, detach the funnel and secure the oil cap.

8. Reattach the spark plug wire

Reconnecting the spark plug wire is the final step. Take the wire’s boot and push it over the tip of the socket once more. Then push it in until it’s fully embedded. Often, you’ll sense or even hear a sound as the connector adjusts to its new position. Once you’ve reconnected your plug, you can reattach any piece you removed to get to it, and you’re finished.

Start the generator and leave it running for a few minutes to make the clean oil circulate in the generator and lubricate it. Turn the generator off after a few minutes and double-check that the oil amount is within the predefined limit. If not, repeat the process above and apply more oil before the required amount is reached.

What Kind of Oil to Use

Change Oil in Generator

For accurate details on proper oil management for your generator, always consult your user manual. The manufacturer would specify the kind of generator oil you require as well as the procedures to follow. The consistency of oil at a given temperature is referred to as viscosity. In general, if you want your generator to operate in incredibly cold conditions, you’ll need a lower-viscosity oil. At extreme heat, on the other hand, you must use a higher-viscosity oil.


Generator maintenance can usually be completed on your own. Checking and maintaining the oil concentrations is one of the most fundamental aspects of generator maintenance. When power disruptions demand operating the generator for long periods, oil levels should be tested frequently. Also, generators must be serviced on an annual basis to ensure that they run smoothly in the long term. It is best to hire skilled technicians to do a full tune-up on generators for an annual inspection.


1. What type of oil should i use in my generator?

Ans. Mineral, semi-synthetic, and entirely synthetic oils are the most common varieties of oil. The type of oil you should use in your generator will be recommended by your generator manufacturer. Modern generators require synthetic oil, while older generators require mineral oil.

2. How often do you change oil on a generator?

Ans. You should replace the oil after the 25 to 30 hours of operation, and then every 100 hours after that. Note that synthetic oils can be replaced even after 200 hours of operation.

3. Can you change your oil without changing the filter?

Ans. You might change the oil in the generator without replacing the oil filter if you want to. Only note that the old oil filter probably wouldn’t be able to strip pollutants from the oil in the generator efficiently.

About the author

Jamie Masterson

With decade-long experience as a generator technician, Jamie has worked with USA’s top generator manufacturers and suppliers as an independent contractor.

The long years of service to the industry has taught Jamie the ins and outs of troubleshooting, repairing, and maintaining all kinds of generators in home, industrial and outdoor settings.

Jamie thinks this platform is a great opportunity to share his tips and tricks with you so you can make the most of such power equipment for better living.

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