To winterize a portable generator you’ll store until spring, fill the tank with fresh gas and fuel stabilizer, run it for about 10 minutes, then drain the carburetor (or drain the tank and carburetor if it will sit a year or more). Change the oil, add a teaspoon or so of oil through the spark plug hole, and store it upright in a cool, dry place. If you need the generator for winter outages, keep it ready instead: fresh stabilized fuel, cold-weather oil, a charged battery and a clear exhaust. Home standby generators need a fall service and, in cold climates, battery and oil warmers.
Storing it or keeping it ready?
There are two kinds of “winterizing,” and they’re almost opposites:
- Storing it for the season. Camping and RV generators that won’t run until spring. The goal is to keep fuel from going stale in the carburetor.
- Keeping it ready for outages. Home backup generators that may need to start on the coldest night of the year. The goal is easy cold starts.
How to winterize a generator for storage
Honda’s fuel guidance for its EU generators and Champion’s storage instructions follow the same basic steps. Always check your own owner’s manual too.
- Treat the fuel. Fill the tank with fresh gasoline and add fuel stabilizer, following the stabilizer’s directions. Honda notes that a full tank helps, because air in a partly empty tank speeds up fuel breakdown. Stabilizer won’t fix gas that’s already stale.
- Run it for about 10 minutes. This pulls treated fuel through the fuel lines and carburetor.
- Drain the carburetor. For storage longer than a couple of months, Honda says to drain the carburetor float bowl. The small amount of fuel there goes bad faster than the fuel in the tank. Many generators have a drain screw on the bowl. Others let you shut the fuel valve and run the engine until it stops.
- For a year or more, drain the tank too. Use a hand pump or the carburetor drain into an approved container. Never drain fuel indoors or near a flame.
- Change the oil. Used oil contains acids and moisture that can corrode the engine while it sits. Use the oil your manual recommends. Here’s what kind of oil a generator uses.
- Protect the cylinder. Honda’s EU2200i manual says to pour about a teaspoon of clean oil through the spark plug hole and crank the engine a few times before reinstalling the plug. Champion suggests about a tablespoon. This coats the cylinder wall against rust.
- Clean it and store it. Wipe off dirt and check the air filter. See how to clean your generator. Store it upright in a dry, ventilated spot away from flames and pilot lights, under a breathable cover instead of plastic.
Propane-only generators are simpler. Propane doesn’t go stale or gum up the carburetor. Close and disconnect the tank, store the cylinder outdoors upright, and change the oil. Dual fuel generators that ran on gasoline still need the gas steps above.
How to winterize a portable generator you’ll use in outages
- Keep stabilized fuel on hand. Add stabilizer every time you fill a gas can. Rotate the gas into your car within the time the stabilizer’s label allows.
- Switch to cold-weather oil if your manual says so. Generac’s portable generator oil chart recommends SAE 30 above 32°F, 10W-30 from -10°F to 40°F, and synthetic 5W-30 in all temperatures. Thick oil in the cold can make a generator hard to pull over.
- Start it once a month. Run it for 15 to 20 minutes with a small load. This keeps fuel moving, charges the battery on electric-start models and shows you problems before an outage does.
- Keep the battery charged. Cold weakens batteries. A battery maintainer helps on electric-start models stored in a cold garage.
- Plan where it will run. Never run it in a garage, even with the door open. Keep it well away from the house with the exhaust pointed away. Here’s how far a generator should be from your house, and how to run one in rain or snow.
- Clear snow and ice. Check the air intake and exhaust before starting. Snow packed around a running generator can block cooling air.
How to winterize a home standby generator
- Get a fall service. Have a dealer change the oil and filter, check the spark plugs and air filter, and test the battery and transfer switch, or do it yourself if you’re qualified.
- Use the right oil. Generac recommends its full synthetic 5W-20 Gaseous Engine Oil for home backup generators, with synthetic 5W-30 as an alternative, according to its home generator oil guide.
- Add cold weather accessories. Generac suggests battery, oil filter and battery pad warmers in places where temperatures regularly fall below 32°F, and a breather warmer for sub-zero or icy climates, per its cold weather kit page.
- Clear the area. Trim plants and remove leaves around the enclosure, and keep snow drifts away from the vents.
- Watch the exercise cycle. Standby generators start themselves on a schedule to stay ready. If you hear it skip a test, check the controller for an alarm.
Getting a stored generator ready again
- Check the oil level and top off if needed.
- Reinstall or check the spark plug.
- Fill with fresh, stabilized gas.
- Start it outdoors and let it warm up before adding a load.
If it won’t start, the most common cause is old fuel in the carburetor. See our list of reasons a generator won’t start.
Related guides: 8 Generator Maintenance Tips for safe extended use, How to Transport a Generator Safely and How to Break In a New Generator.
FAQ
Should I drain the gas from my generator for winter?
For one or two months, a full tank of stabilized fuel is usually enough. For longer storage, drain the carburetor. For a year or more, drain the tank and carburetor.
Can I leave my generator outside in winter?
It’s better stored in a dry shed or garage, with the engine off. If it has to stay outside, keep it off the ground and under a ventilated cover or generator shed. Never run it in a garage.
What oil should I use in a generator in winter?
Follow your manual. Many manufacturers recommend 10W-30 or synthetic 5W-30 for cold weather.
How often should I run my generator in the winter?
About once a month for 15 to 20 minutes, with a small load, if you’re keeping it ready for outages.