A generator that is not properly maintained will fail when you need it most — during a power outage, a storm, or an emergency. The good news is that generator maintenance is straightforward, inexpensive, and takes less time than most people expect. Follow this guide and your generator will start reliably every time for a decade or more.
Maintenance Schedule Overview
| Task | Frequency |
|---|---|
| Check oil level | Before every use |
| Run the generator | Monthly (at least) |
| Change oil | Every 50–100 hours or annually |
| Replace air filter | Every 100 hours or annually |
| Replace spark plug | Every 100 hours or annually |
| Clean fuel system | Before long-term storage |
| Load test | Every 6 months |
Step 1: Check and Change the Oil
Engine oil is the single most important maintenance item for any generator. Running a generator with low or dirty oil is the fastest way to destroy the engine — and it is completely avoidable.
Before every use: Check the oil level with the dipstick. The oil should be between the minimum and maximum marks and should appear amber to light brown in color. Dark, gritty oil needs changing immediately.
Oil change interval: Change the oil every 50 hours of operation for the first 20 hours (break-in period), then every 100 hours or once per year — whichever comes first. Most residential generators use SAE 10W-30, but always check your owner manual for the manufacturer recommendation.
How to Change Generator Oil
- Run the generator for 5 minutes to warm the oil (warm oil drains more completely)
- Turn off the generator and let it cool for 10 minutes
- Place an oil drain pan under the drain plug
- Remove the drain plug and allow oil to drain completely
- Replace the drain plug, add fresh oil to the correct level
- Dispose of used oil at an automotive store or recycling center
Step 2: Replace the Air Filter
A clogged air filter restricts airflow to the engine, causing it to run rich, produce excess carbon, and lose power. Replace the air filter every 100 hours of operation or annually.
Most generator air filters are foam or paper elements that cost under $10. Check the filter visually — if it is dark gray or black, replace it regardless of hours. If you operate the generator in dusty conditions, inspect and clean the filter more frequently.
Step 3: Check and Replace the Spark Plug
A worn or fouled spark plug causes hard starting, rough running, and increased fuel consumption. Spark plugs should be replaced every 100 hours or annually. Replacement plugs typically cost $5–$15.
When inspecting a spark plug, look for black carbon deposits (running rich or oil contamination), white or gray deposits (running lean), or electrode wear. A properly functioning plug will have a light tan or gray color on the electrode.
Step 4: Run the Generator Monthly
This is the maintenance step most people skip — and it causes more problems than any other. Generators that sit unused for months develop stale fuel, gummed carburetors, and dead batteries (on electric start models).
Run your generator under load for at least 30 minutes every month. Connect a few lamps, a fan, or other appliances to create a realistic load. This keeps the fuel system clear, charges the battery, exercises the engine, and lets you catch any problems before you actually need the generator.
Step 5: Fuel System Care
Use Fresh Fuel
Gasoline begins to degrade after 30 days. Old fuel is the number one cause of generator starting problems. Use fuel within 30 days of purchase, or add a fuel stabilizer like STA-BIL if the generator will sit for longer periods.
Before Long-Term Storage
If storing the generator for more than 30 days, either add fuel stabilizer and run the engine for 10 minutes to distribute it through the system, or drain the fuel completely from both the tank and carburetor. A carburetor with old, gummed fuel is the most common generator repair — and it is entirely preventable.
Step 6: Check the Battery (Electric Start Models)
Electric start generators have a small battery that powers the starter motor. These batteries discharge over time when the generator sits unused. Check the battery voltage every 3 months — it should read 12.6 volts or higher. If the battery drops below 12 volts, charge it with a battery maintainer. Replace the battery every 2–3 years as preventive maintenance.
Generator Maintenance Checklist
- Check oil level before every use
- Change oil every 100 hours or annually
- Replace air filter annually
- Replace spark plug annually
- Run under load for 30 minutes monthly
- Use fresh fuel or add stabilizer
- Drain fuel before storage over 30 days
- Check battery every 3 months
- Inspect all connections and outlets annually
Follow this maintenance schedule and your generator will provide reliable power for 10, 15, or even 20 years. The cost of a few quarts of oil and a spark plug each year is nothing compared to the cost of a new generator — or the cost of being without power when you need it most.