How Often Should I Change the Oil in My Generator?

Your generator’s engine has moving parts such as pistons and valves. These parts are in constant motion and require oil for lubrication. However, the oil collects dirt from the engine components necessitating replacement. But how often should I change the oil in my generator?

Portable generators require an oil change after 100 hours of use. If you have a Diesel Generator, replace the oil after 250 hours. However, Standby generators do not have regular intervals. You should change their oil after repairs and servicing. Additionally, oil servicing routines depend on the purpose and brand of the generator. 

This article explains the when and how of changing the oil in your Generator’s Engine.

When should I change the Oil in My Generator’s Engine?

1. After Running for the First Time

When running your generator for the first time (break-in), you should change the oil after the first 5-8 hours. This range depends on your manufacturer. If unsure, refer to your manual for the exact duration.

Some manufacturers do not ship Generators with oil. Confirm this from the packaging or manual. If so, refer to the manual on what type of oil you should use. In both cases, check the duration after which you should change the oil when operating for the first time.

After the Oil fill or replacement, use a dipstick and ensure the level is exact. Underfilling or overfilling will damage Engine and Generator Parts.

2. After long runtimes

Portable generators handle small power loads thereby needing an oil change after 50 -100 hours. If your generator runs for long hours, you should change the oil after 50 hours. Otherwise, 100 hour-intervals are sufficient.

Standby generator’s oil should be changed after servicing, repairs or leakages.

Diesel generators require an oil change after 250 hours of use.

3. When your Generator has malfunctioned

After fixing malfunctions in your generator, you should change the oil. Otherwise, the dirty oil will damage the generator.

4. After leakages and spills

How Often Should I Change the Oil in My Generator?When changing fuel, spilling fuel on the crankcase or oil filter will dilute your engine oil. This contamination will reduce its lubricating properties; corroding the engine parts. While in transit, fuel may leak into the crankcase. You should ensure the fuel valve is tightly closed to prevent leakages.

5. After a weather hazard

Storms and floods make Grime and debris accumulate on the crankcase or oil filter. This contaminates the oil in Generators anchored to the ground prompting an oil change.

How Can I change my Generator’s Oil?

How Often Should I Change the Oil in My Generator?When changing oil, you also need to change the filter. Oil filters trap dust and debris from the Oil taken into the engine chambers. Any foreign object in the engine can knock it or cause wear and tear between moving parts.

Changing the Oil and Oil Filter

Materials required:

  • New oil filter
  • New, clean Oil


  • Servicing Manual.

Ensure the generator has been inactive for 24 hours for cooling. The residue oil in the filter can cause high-degree burns.

Step 1 – Drain dirty Oil from the Generator’s Engine

Locate the Engine Oil Drain. For portable generators, it’s on the front lower side; below the engine panel. Refer to your manual for diesel and standby generators.

It’s covered with a threaded cap. Open the cap and attach a rubber hose to the draining outlet using a threaded barbed fitting. Ensure the engine fuel valve and the crankcase are closed.

Place a trough or bucket to drain the dirty oil. Check your manual to know the capacity of your filter and what size of draining vessel you will need. Open the engine curbside access door and turn on the engine oil valve. This will drain the oil from the filter. Turn off the oil valve.

Step 2 – Uninstall the Old Filter

Using a Banded Filter Wrench, twist the filter gently in a clockwise manner until it’s loosened. You can now use your hand to turn it until release. You should have your draining vessel ready for residue oil from the filter.

Ensure the “O”-ring comes out with the filter. Remove the draining hose and replace the threaded cap. Close the Engine Oil Valve.

Step 3 – Install the New Filter

Take your new filter and lubricate its O-ring using new, clean oil. Install the new filter by hand until it’s fitted. Do not use the wrench or overtighten; it will damage the O-ring.

Step 4 – Fill the Filter with Clean Oil

Open the cap close the oil fill tank and insert a funnel. Fill it with new, clean oil. Use a dipstick and ensure the level aligns with the specifications in the generator’s manual.

Replace the cap. Check for any leaks and wipe off excess oil. Start the engine and let it run for 5 minutes. This will circulate oil in the new filter.

You have changed your Generator’s oil.


For a portable generator, change the oil after 50-100 hours of use. If you have a diesel engine, service it after 250 hours. When changing your engine oil, you should replace the oil filter too.

Refer to your Generator’s manual before any servicing and for compatible products to us with your generator.

Faqs About How Often to Change Generator Oil

How Do I Know If My generator needs oil?

When the Oil is dirty or has leaked, the engine will start to produce cranky noises and break down. You should check the oil and change or refill.

How many hours should you change generator oil?

You should change your engine’s oil after 50-100 hours.

How often should a generator be serviced?

You should service your generator after 300 hours of use or 6 months. Servicing includes changing your generator’s oil and filters.

How long can you leave the oil in your portable generator?

50-100 hours. If your generator runs longer than 3-6 hours, you should change the oil after 100 hours.

How often should I check generator oil?

Using a dipstick, you should check your Generator’s oil after 100 hours.

Can you put oil in a generator while it’s running?

No. Vibrations from the running engine will cause oil to spurt causing eye accidents.

Additionally, the oil tank is under high-temperature heating oil. Accidental spurts or leakages may cause 2nd-3rd degree burns.

Which Oil is best for the generator?

For cold places with long winters, you should use synthetic generator oil and Castrol products. They can withstand cold temperatures.

If you’re in a hot area, you can use Honda or shell oil products. They are optimized for air-cooled engines.

For mild climates, Briggs and Stratton oil products work best.

In case your manufacturer has an oil products’ line (Honda and Generac), that’s the recommended choice. During manufacture, their engines are optimized for those oil products.

Where do you put oil in a generator?

You should fill your engine with oil through the oil cap. It’s located on the front lower side of the generator. Refer to your manual in case you have a standby or Diesel generator.

Is Synthetic Oil better for generators?

Yes. It works well under a range of temperatures and does not form sludge.

Must I use a brand-specific Generator?

No. It’s however recommended to use Spare parts and oil from a parent brand.

Using a different brand or type will not damage your generator; only reduce its efficiency

How long should I run my Generator for maintenance?

300 hours or 6 months. You should change the oil, fuel, and air filters and repair any mechanical issues in your Generator after 200-300 hours.

Can I Re-use Oil from my Car in my engine?

No. The oil drained from a Car’s engine has dirt and debris that will corrode your Generator’s Engine. Additionally, oil products for Car engines differ from those manufactured for generator engines.

Are Generators Shipped with Oil?

No. This is to prevent leakages and spills which may cause a fire while in transit.

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About Steve Stuart

Steve Stuart is an electrical engineer who developed interest on generators during his school years. After school, he became a generator enthusiast. This is after encountering power supply problems at the area of residence where he lived. Power would be on and off and so food would go bad and the room heater would go off especially during winter. After trying the different generator brands for several years, Steve now provides information on the available brands and products in the market today. Based on his experience, he gives the do’s and the don’ts when it comes to generator use.

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