[red-beard]

They are air-cooled lawn-mower engines.

Splash lubricated
Low compression with not exactly well sealing rings
Magneto type ignition
Not well speed regulated

On the pressure lubricated generator-engines with filters, they are good for about 100 hours, then you change the oil.

Think about a car engine. What is the average speed you drive over a week? Not highway speeds. Probably closer to 30-40 miles per hour. At 30 miles per hour, 3000 miles = 100 hours of engine operation. My Honda manual said if most driving is highway, 7500 miles is good for an oil change. 7500 miles at 65 miles per hour = 115 hours.

I expect if you were to switch to a C-D ignition and use better plugs, natural gas fuel, a MUCH better lube oil filter, you could get more hours. But these engines are not designed for continuous running long life.

One of the reasons our hybrid system works well is that you run the engine only a few hours a day. Instead of 100 hours = 4 days, at 3 hours per day you are about a month between oil changes. If you upsize some of the solar and batteries, then you may only run the generator on cloudy days and get 3 months between oil changes.