Generator Oil Change Guide
In This Guide
Oil is the single cheapest way to protect a generator's engine, and the generator oil change is a job any owner can do in fifteen minutes. It matters more on a generator than most machines, because a generator often runs for many hours straight under heavy load during an outage, which is exactly when clean oil earns its keep. Here is which oil to use, how often, and how to change it properly.
Which Oil Your Generator Needs
Most small generator engines use a high-quality detergent oil meeting the SAE service classification in the manual. The right viscosity depends mainly on the temperature you run it in.
| Oil | Best for |
|---|---|
| SAE 30 | Warm weather, typical summer running |
| 10W-30 | A wide temperature range, varying conditions |
| Synthetic 5W-30 | Cold weather and extended protection |
How Often to Change It
Generators have a distinctive oil schedule because of how hard they can run.
- First change: after the first 20 to 30 hours on a brand new generator. This break-in change is important and often skipped.
- Routine: every 100 hours of running, or once a year, whichever comes first.
- During a long outage: every 50 to 100 hours, because continuous heavy load ages oil fast.
That outage interval is the one people miss. Three days of continuous running can pass 50 hours, so a generator worked hard through a storm may need fresh oil before the storm is even over.
What You Will Need
The right oil and the correct quantity for your engine, a drain pan, a funnel, a socket or spanner for the drain plug, clean rags, and gloves. Check your manual for the exact oil capacity, which is usually small, often around half a litre to a litre on portable units.
How to Change Generator Oil
1. Warm the engine briefly
A few minutes of running thins the oil so it drains fully. Then stop the engine and disconnect the spark plug lead.
2. Position the drain pan
Under the oil drain plug.
3. Remove the drain plug
And let the old oil drain completely. Tilting the generator slightly can help it drain fully, if the design allows.
4. Refit the plug
Clean it and reinstall, snug but not overtightened.
5. Refill to the correct level
Add the specified oil slowly through the filler, checking the dipstick as you go. Stop at the full mark.
6. Check and run
Reconnect the spark plug lead, start the engine, check for leaks, then recheck the level.
Dispose of the Old Oil Properly
Used oil is hazardous waste and must never go in the trash or down a drain. Most auto parts stores accept used motor oil free of charge. Collect it in a sealable container and take it there.
Oil and the Low Oil Sensor
Nearly every generator has a low oil sensor that stops the engine if the level drops too low. It is a protective feature, and it is a common reason a generator will not start or cuts out. Keeping the oil at the correct level is not just good maintenance, it keeps that sensor happy and the generator running.
Rather Have a Real Technician Handle It?
A Wildwood technician comes to your home, diagnoses the generator on site, and gets it running, usually in about an hour. More than 10,000 repairs completed since 2019, with flat rates quoted before we arrive so there are no surprises. When you need power back, you need it back now.