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I think this is on-topic after reading the FAQ, so I figured I'd go ahead and ask.

I gave my gas generator its scheduled 3-month interval "workout" last night, and after letting it run for about 30 minutes, I turned the fuel valve off and let it run until it died so there wouldn't be any gas left in the fuel lines. I use ethanol-free gas with Sta-Bil added to it. Then I siphon out whatever's left in the tank after the generator has been shut down. However in the last few seconds it was running, the whole generator started shaking and making a terrible racket. Should I not do this - am I putting more wear on the engine than I would by letting old gas sit in the fuel lines?

I've heard what seems to be conflicting results in running engines out of gas. For cars it's bad, but the overwhelming online opinion for generators seems to be that running them dry before storage is the best option. Is this because automobile fuel pumps can be damaged by running dry, but since generators are usually gravity-fed, it isn't harmful to them?

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I recommend to everyone I know to run your generator or other small equipment dry before storage. The main purpose of this is to get all of the ethanol based fuel out of carburetor and fuel bowl. Ethanol has a propensity of gumming things up and can leave a lot of varnish over time. This tends to plug orifices needed for proper fuel metering while running, and thus kills the carb. I've unsuccessfully attempted to rebuild small engine carbs, but found it much easier/cheaper (time vs. cost) to replace. I have had to replace two carbs out of three small equipment pieces with gas engines. Since I started running them dry, I've had no issues. Starting takes a few more pulls of the cord, but once the bowl fills, they fire without too much hassle.

As far as the bucking goes, this would be normal as the bowl runs out of fuel. As long as you do not have a load on your generator when you do this, it should not cause any issue.

One other thing for proper maintenance. When giving your generator a "workout", make sure you plug something into it and run it. Something which will actually put a load on the generator. Generators are built to work. They tend to not like to just "run" ... for some reason this tends to wear them out quicker. You are running it anyway, so plugging something into it and running it should not cause you any concern. I run a 15A shop vac on mine, which is a 5250w running generator. Gives it a little bit of a workout.

EDIT: You may also want to look at this post, this post, and maybe even this post ... all from this SE site.

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Even non ethanol gas with Sta-Bil has a shelf life. Fresh fuel is better than older treated fuel and is a cheap investment. I add any fuel older than 60 days to my vehicle and use fresh fuel in the small engines. –  mikes Feb 12 at 1:52

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