Portable generator maintenance: a schedule that keeps it ready for the next outage

A generator is the one appliance most people only use when everything else has gone wrong. That's exactly why it fails: it sits for a year, the fuel goes stale, the battery dies, and the first pull of the cord happens in the dark during a storm. A little maintenance on a schedule prevents nearly all of that. This guide lays out what to do and when, using a real manufacturer's schedule as the baseline.

Your own owner's manual is the authority for your machine. Intervals vary by engine, and following the manual protects your warranty. Use this guide to understand the why, and to build a routine.

A real maintenance schedule, from the manual

Honda's owner's manual for its popular EU2200i inverter generator gives a typical schedule for a small four-stroke engine. Each item is due at the month or operating-hour interval, whichever comes first:

Task	Interval
Check engine oil level	Before each use
Change engine oil	After the first month or 20 hours, then every 6 months or 100 hours
Check air cleaner	Before each use
Clean air cleaner	Every 3 months or 50 hours (more often in dusty conditions)
Check and adjust spark plug	Every 6 months or 100 hours
Replace spark plug	Every year or 200 hours
Clean spark arrester	Every 6 months or 100 hours
Valve clearance check	Every year or 200 hours (dealer service)
Clean fuel tank and filter	Every year or 200 hours (dealer service)
Check fuel tube	Every 2 years, replace if needed (dealer service)

Two things are worth noticing. First, the break-in oil change at one month or 20 hours is the most important single service. New engines shed fine metal particles as they wear in, and changing that first oil early protects the engine for its whole life. Second, the calendar intervals matter even if you barely use the generator. Oil breaks down and absorbs moisture over time, so a generator that ran 10 hours this year still needs its six-month oil change.

Larger open-frame generators and standby units follow similar logic with different numbers. Look up the table in your manual and copy it onto a card taped to the generator.

Keep an hour log

Many inverter generators have no hour meter. A cheap clip-on hour meter, or a simple log of date, hours run and service done, tells you when the 50- and 100-hour items come due. During a long outage you can reach 100 hours in four days, which means an oil change in the middle of the event. Keep oil, a funnel and a drain pan with the generator so that's a ten-minute job, not a trip to a closed store.

Exercise it between outages

A generator that only runs during outages will have problems at the worst time. Running it on a schedule:

• keeps seals and gaskets lubricated;
• moves fresh fuel through the carburetor, which is where varnish from old fuel usually causes trouble;
• charges the starting battery on electric-start models;
• reveals problems while you have time to fix them.

A practical routine is to run the generator once a month for 15 to 30 minutes, under some load. Plug in a work light, a space heater or a shop vacuum so the engine actually works. Running with no load at all doesn't heat the engine fully. Follow your manual if it gives a specific exercise routine.

Always run it outdoors, in the same spot you'd use in an outage, far from doors, windows and vents. The CPSC warns that portable generators should never be run inside a home, garage, basement, crawlspace or shed, even with the door open.

Fuel is the most common failure

Most "it won't start" problems trace back to stale gasoline. Ethanol-blended gasoline can begin to break down within a few months, leaving gum and varnish that clog the tiny passages in a carburetor. Your options:

• Stabilize every can. Add fuel stabilizer when you buy gasoline, following the label, and run the engine a few minutes so treated fuel reaches the carburetor.
• Rotate fuel. Pour stored gas into your car every few months and refill the cans.
• Drain for long storage. Many manuals recommend draining the tank and carburetor before storing more than a month or two. On some models, you turn the fuel valve off and let the engine run until it stalls.
• Use propane. If you have a dual-fuel model, propane doesn't go stale. Our guide to propane vs. gasoline covers the trade-offs.

See our guide to storing generator fuel for containers and quantities.

Battery care on electric-start models

Electric-start generators have a small battery that slowly discharges in storage. If the generator has a charging port, keep it on a battery maintainer, or charge it every month or two. Exercising the generator monthly also recharges it. Keep the recoil cord working as a backup.

Seasonal storage checklist

Before putting the generator away for more than a month:

1. Change the oil if it's near the interval, so the engine sits with clean oil.
2. Stabilize and run the fuel, or drain the tank and carburetor as the manual says.
3. Clean the air filter and the outside of the generator.
4. Check the spark plug, and replace it if it's due.
5. Store it dry and covered, in a place with ventilation, never where fuel vapor could reach a pilot light or flame. NFPA advises storing fuel outside living areas.
6. Write the date and hours in your log.

Pre-storm checklist

When a hurricane, ice storm or wildfire season is forecast, do this a few days ahead:

• Start it and run it under load for 15 to 30 minutes.
• Check the oil and top up. Have enough oil on hand for at least one change.
• Get fresh fuel for several days, stabilized, or fill propane cylinders. Our fuel runtime estimator helps you work out how much.
• Check cords. Use heavy-duty outdoor extension cords rated for the load, with no cuts or damaged plugs. Our guide to extension cords for generators explains gauge and length.
• Test your transfer switch or interlock if you have one. Never backfeed through a dryer outlet. Our guide to transfer switches vs. interlocks explains why.
• Test CO alarms inside the home and replace batteries.
• Pick the spot where the generator will run, well away from the house, and think about how you'll keep it dry without enclosing it.
• Print your load plan. Decide which appliances you'll run and in what order. Our outage prep checklist builds one for you.

During a long outage

• Check the oil every time you refuel. Small engines can burn oil under heavy load.
• Turn the generator off and let it cool before refueling. OSHA and the CPSC both warn that fuel spilled on hot engine parts can ignite.
• Change the oil at the hour interval, even mid-outage.
• Keep the air intake clear of leaves and snow.

Signs it needs a repair shop

Get professional service if the generator:

• surges or hunts even after fresh fuel and a clean air filter (often a carburetor problem);
• produces voltage that's too high or low, or won't hold the load it's rated for;
• leaks fuel or oil;
• smokes heavily, knocks, or loses compression.

Valve clearance and internal fuel-system cleaning are dealer jobs on most small generators.

The short version

• Change the oil after the first 20 hours, then on the manual's schedule, by hours or months, whichever comes first.
• Run it monthly under load, outdoors.
• Never let untreated gasoline sit in it.
• Keep oil, a filter, a spark plug and fresh fuel ready before storm season.