The usual generator oil type for a portable gasoline generator is a 4-stroke detergent oil in SAE 10W-30, but the right grade depends on the manufacturer and the outdoor temperature. Honda recommends 10W-30, Generac matches SAE 30, 10W-30 or synthetic 5W-30 to temperature, and Generac air-cooled home standby generators take 5W-20 full synthetic after break-in. Check your owner’s manual.
What oil does each generator brand recommend?
| Generator | Recommended oil | Temperature guidance | Synthetic |
|---|---|---|---|
| Honda portable (EU3000is manual) | SAE 10W-30 for general use, 4-stroke automotive detergent oil, API SJ or later | The manual gives a temperature chart for choosing between 10W-30, 5W-30 and SAE 30; check it for your climate | Allowed if it meets all of Honda’s oil requirements; change intervals still apply |
| Generac portable | SAE 30, 10W-30 or synthetic 5W-30 | SAE 30 above 32°F; 10W-30 from -10°F to 40°F; synthetic 5W-30 at all temperatures | Only after break-in on the supplied petroleum oil |
| Champion portable (5500 W dual fuel manual) | 10W-30 automotive oil for typical use | A chart in the manual for extreme temperatures; full synthetic 5W-30 aids starting below 41°F | After the 5-hour break-in; does not extend the change interval |
| Generac air-cooled home standby | Generac 5W-20 full synthetic (GEO) after break-in | All temperatures | Ships with conventional 5W-30 for break-in only |
Note that Generac says its 5W-20 GEO oil is a proprietary blend designed for natural gas and propane home standby generators, not for portable units. For standby units, Generac lists other oils only as emergency alternatives when GEO is not available, meeting API SJ, SL or better:
- Synthetic 5W-30 for the full temperature range
- 10W-30 from -10°F to 40°F
- SAE 30 above 32°F
Liquid-cooled standby models have their own specification in the owner’s manual.
Should I use synthetic or conventional oil?
Manufacturers allow synthetic oil but attach conditions:
- Break in on conventional oil first. Generac says to use the supplied petroleum oil for break-in before switching to synthetic on its portables, and its standby units ship with conventional 5W-30 for break-in. Champion allows synthetic only after its 5-hour break-in.
- Synthetic does not stretch the interval. Honda says its engines are developed and certified with petroleum-based oils, that synthetic may be used if it meets all the oil requirements, and that recommended change intervals must still be followed. Champion says the same about intervals.
- Why choose synthetic. Generac’s standby oil FAQ says synthetic oil is more highly refined and protects better at low and high temperatures, while conventional oil is more likely to form deposits and sludge.
- Do not mix oils. Generac advises against mixing types or brands except in a true emergency, followed by a full oil change as soon as possible.
Oil specs for generators in our catalog
Where our product listings state an oil grade or capacity, here is what they say. Treat capacity as a guide: fill to the level the dipstick or filler neck shows in your manual, and never overfill.
| Generator | Oil as listed | Oil capacity as listed |
|---|---|---|
| DuroMax XP2300iH | 10W-30 (blended, conventional or synthetic) | 13 fl oz |
| DuroMax XP5500HX | 10W-30 (blended, conventional or synthetic) | 20.3 fl oz |
| DuroMax XP13000HXT | 10W-30 (blended, conventional or synthetic) | 40.5 fl oz |
| DuroMax XP15000HXT | 10W-30 (blended, conventional or synthetic); oil filter STP S2878XL | 57.5 fl oz |
| Generac GP Series 12,500 W tri-fuel | 10W-30 / SAE 30 (engine oil included) | 1.06 qt (1.0 L) |
| Tomahawk 2000W inverter | SAE 10W-30 | 0.4 qt |
| Tomahawk 5500W inverter | SAE 10W-30 | 0.7 qt |
| Honda EU1000i | Not stated in the listing; see the Honda manual | 8 oz |
The Generac GP8000E ships with engine oil and an oil funnel in the box. Others arrive dry: Honda’s EU3000is manual says that generator is shipped without oil, so check before the first start. The low-oil shutdown will stop the engine if you forget, as our generator won’t start guide explains.
How often should I change generator oil?
| Generator | First change | Then |
|---|---|---|
| Honda EU3000is | First month or 20 hours | Every 6 months or 100 hours |
| Generac portable | After 20 to 30 hours, by model | Every 100 hours; the GP Series manual adds every year, and monthly under heavy load or high temperatures |
| Champion 5500 W dual fuel | After 5 hours | Every 100 hours or annually; every 50 hours under heavy load or in hot environments |
| Generac air-cooled standby | 25 hours (20 hours on the 7.5 kW PowerPact) | Every 200 hours, every 100 hours below 40°F or above 85°F, and at least every 2 years |
Every manufacturer here says to check the oil level before each use of a portable. For the full service list, see our generator maintenance schedule.
How do I change the oil in a portable generator?
- Work outdoors with the engine off. Generac’s GP Series manual says to disconnect the spark plug wire when working on the unit, and to let the engine cool before draining to avoid burns. Honda says to drain while the engine is still warm so the oil drains completely, so aim for warm, not hot.
- Set the generator on a level surface.
- Place a container under the drain.
- Remove the drain plug and the filler cap.
- Let the oil drain.
- Reinstall the drain plug. Honda specifies a new sealing washer on the EU3000is.
- Refill with the recommended oil to the upper limit shown in your manual. Do not overfill.
- Take used oil to a recycling center in a sealed container. Honda says never to put it in the trash, on the ground or down a drain.
How do I change the oil in a Generac home standby generator?
Generac says owners can change the oil themselves following the manual, or have a certified Generac dealer do it. Its steps for current air-cooled Guardian and Next Generation units, in short:
- Run the unit in MANUAL for 3 to 5 minutes to warm the oil, then press OFF and let it cool. If you are doing this during an outage, follow Generac’s outage shutdown and breaker steps first.
- Remove the front panel.
- Free the oil drain hose from its clip.
- Remove the cap and drain the oil.
- Remove the oil filter.
- Hand-tighten the new filter until the gasket touches the adapter, then add three-quarters to one full turn.
- Add the amount of oil your manual lists.
- Run in MANUAL for one minute and check for leaks.
- Press OFF and wait five minutes.
- Check the dipstick and top up without overfilling.
- Replace the panel and return the unit to AUTO.
During extended outages, Generac says to shut the generator down every 24 hours to check the oil. Liquid-cooled units, and anything beyond these steps, are best left to a dealer. See our standby generators for current models.
What does a Generac maintenance kit contain?
Generac says the correct standby kit depends on engine type, kilowatt rating and production year, and warns that using a kit on an unlisted model can cause damage and affect the warranty. The kits in our Generac maintenance kits range list these contents:
- Generac GNC-6485 (20 to 22 kW air-cooled Guardian, 999cc, 2013 and later): air filter, oil filter, two spark plugs, oil funnel, chamois, instruction manual.
- Generac GNC-5664 (12 to 18 kW air-cooled, built before 2013): the same parts plus a maintenance reminder sticker.
- Generac GNC-5984 (36 kW, turbocharged 2.4L): air filter, oil filter, four spark plugs, funnel, chamois, reminder sticker.
- Generac 7991 (liquid-cooled 4.5L: 48 kW Protector QS, 60/80 kW Protector): air filter, oil filter, four spark plugs, funnel, chamois, sticker, owner’s manual.
- Generac 5720 for the 530cc engine in the XP10000E and XG10000E portables.
None of these listings include oil in the contents. Generac says some of its kits include oil and others do not, so plan to buy the specified oil separately. In cold climates, the Generac 7103 breather heater kit for air-cooled standby models built after 2013 requires 5W-30 synthetic oil once installed.
Frequently asked questions
What kind of oil does a generator take?
Most portable gasoline generators take a 4-stroke detergent oil, usually SAE 10W-30 for general use, with other grades allowed by temperature. Generac air-cooled home standby units take Generac 5W-20 full synthetic after break-in. Check the manual for your model.
Can I use synthetic oil in my generator?
Generally yes, after break-in. Honda allows synthetic oil that meets its requirements, and Generac and Champion approve synthetic 5W-30 for their portables. It does not lengthen the change interval.
Can I use 5W-20 oil in a portable generator?
Not Generac’s 5W-20 GEO, which Generac says is designed for natural gas and propane home standby generators, not portable units. Use a grade from your portable’s manual.
How often should I change generator oil?
It depends on the maker: Honda’s EU3000is every 6 months or 100 hours, Generac portables every 100 hours, Champion every 100 hours or annually, and Generac air-cooled standby units every 200 hours and at least every 2 years, each after an earlier break-in change.
Sources
- Honda: EU3000is generator owner’s manual
- Honda Engines: FAQ (synthetic oil)
- Generac: What type of oil is recommended for Generac portable generators?
- Generac: How often should the oil be changed in a Generac portable generator?
- Generac: GP Series multi-fuel portable generator owner’s manual
- Generac: What type of oil should I use in my home backup generator?
- Generac: Home standby generator oil FAQ
- Generac: How do I change the oil and oil filter in an air-cooled home standby generator?
- Generac: Yearly maintenance for a home standby generator
- Generac: Where can I find a maintenance kit for my Generac generator?
- Champion: 5500W dual fuel portable generator operator’s manual (model 100231)