Old post but commenting still active so here's how I've kept my little Champion inverter generator alive for the past 13 years:

1. I only buy ethanol free, Top Tier gas, and I store it in metal cans. Try to buy the "summer blend" gas if your area switches from summer to winter blend. The summer blend gas stores better because it has less volatile components. I label the cans with the purchase date and rotate it every 12 months no matter what. I use it for the mower, also 13 years old and still running great btw. Put the gas near the end of its 12 months into the car if it shows zero signs of oxidation. Get good quality gas cans like the metal ones that are non vented.

2. Add some Stabil Marine Fuel Preservative (the blue juice) to all your cans prior to filling with gas.

3. I put a "toe tag" card on the generator and mark down when I serviced it and ran it last. If I didn't write it down, it didn't happen.

4. Exercise it quarterly. I do every 3 months. Fuel it up with about 30-60 minutes of fuel, start it up. Should start with just a few pulls once the carb is primed. I let it warm up for a few minutes with no load, then put 1600 watts load on mine (that's the max). Write down the date you ran it on the toe tag card you have on the generator.

5. While running, I check the voltage and frequency to verify it's correct at idle and under full load. I want the voltage drop to be modest and appropriate, but the frequency needs to stay close to 60hz. I verify functionality of both outlets (it's a small generator), check the overload protection, verify eco mode works. Just basic function tests.

6. After the generator runs out of fuel, I let it cool, drain remaining fuel from the carb. Check the air cleaner element, verify color and condition of the oil.

7. Every 2 years or 25 hours of run time, I'll change the oil. Use something appropriate for the motor. A quart of supertech full synthetic is so cheap, but any good cheap synthetic oil is fine. Brand doesn't matter. I don't hardly ever need the generator for anything, so I often just have a few hours on the oil at the 2 year mark.

8. Store it elevated off the floor a few feet. This keeps moisture from concrete, water spills, and allows enough air flow to keep it from rusting.

9. It's maybe a hour of work every 3 months.

If you're buying a generator, get the best quality generator you can afford. You want something that will have parts availability for a number of years. I use a large capacity power station so I don't need a large generator. My only use of the generator is to charge the power station, then I use the power station for loads.

The price of power stations and lithium batteries is so cheap, you probably don't need as much generator as you think. You can buy an all-in-one charger, 5kw inverter, mppt device for about $600 now, and a 5.1kwh server rack battery for $800. Or buy a 3+kwh power station for $1400 and expand it to about 6kwh for a total of maybe $2k. Then you only need your generator to refill the power station from time to time and this radically extends your runtime and safety. You can run the generator at it's most efficient output setting (let's say 25-50% of rating) only as long as needed and shut it off. If you have extended outages, this lets you power down the generator while still running your loads off the power station so you can troubleshoot, fuel it when the engine is cold, or change the oil safely.