Is it better to run out of gas periodically vs topping off the tank before each use?

l008com

l008com

Well-Known Member
I'm asking this about lawnmower engines here, but I suppose this also applies to snowblower engines too, and any other gas powered machine.

I usually top off my tank before each use, unless its late in the season and I'm explicitly trying to run the machine down on gas. And I keep my gas clean, and i drain the gas and winterize at the end of the season, and I put a little seafoam in all my small engine gas, so everything seems fine.

But I see so many youtube videos where they drain the carb or the tank and theres so much dirt or water in the fuel. It seems like it would be kind of hard to get water in a lawnmower engine. You'd have to be gassing up in the rain, but most people aren't going to be using their lawnmower in the rain in the first place. But with snowblowers, its very common to have to gas up while its still flurrying out. Or to just have snow everywhere so when you take the cap off, a little falls in.

So if you run it out of gas, the engine is going to suck in at least the water, if not some of the micro-dirt too and 'burn' it up in the engine and sent it out the tailpipe, preventing it from building up in the fuel system.

Is this sound reasoning? Or are there other factors that make this moot? I almost never do this, but it would be easy to start. Especially with a lawnmower. It would be a little more of a hassle to do it with a snowblower given how big and heavy they are (and mine has tracks so you can't push it, you can only drive it when its running).

I wonder what other people's thoughts are on this?
 
If you know that you are using good fuel I wouldn’t worry about it. This is probably a personal preference and there will be people on both sides of this debate. If you are sure you have good fuel is more important to me.
 
I think you are a suspenders and belt kind of guy. Don’t change a thing. What you are doing is working for you.

But you asked about how water got in the fuel tank. As Taryl has often said, outdoor equipment does a lot better when it is stored inside, but a lot of people leave them outside. Rain and snow will find a way into the gas tank, especially if the fuel cap is loose or deteriorated. Even if equipment is inside, if you leave pump gas in the tank, your 10% ethanol fuel will attract water from the atmosphere. Most of the time this small amount of water will simply be burned off as the engine runs. Bear in mind that gasoline is less dense than water, so the water is always at the bottom of the fuel tank. Also keep in mind that a lot of, maybe most, mowers and snowblowers do not have fuel pumps and are gravity-fed. So the stuff at the bottom of the tank is the first to be burned. Yeah, I know that tanks are designed so the outlet is not at the absolute bottom so as to keep dirt, grass, leaves, and water from being sent to the carb. But if there is just enough water in the tank to get into the outlet, it will go first. A little water being combusted will not harm an engine. It will turn to steam and exhaust with the rest of the gases. So no worries about a few drops of rain or snowflakes. But if your carburetor bowl is full of water and stale gas because you left ethanol pump gas in the tank all winter, no amount of Seafoam or other alchemy will make the engine run.

Personally, when I put a machine into storage I run the tank dry and take the bowl off the carb and clean it out. Have done this since I bought my first gas powered mower, except the first year. Learned my lesson in year 2. I also drain the oil while the engine is still hot, and tape a note to the top of the engine saying, “No oil, you idiot!” Has worked so far, but no telling what foolishness I can find a way to wreak on myself.
 
Oddjob said:
I think you are a suspenders and belt kind of guy. Don’t change a thing. What you are doing is working for you.

But you asked about how water got in the fuel tank. As Taryl has often said, outdoor equipment does a lot better when it is stored inside, but a lot of people leave them outside. Rain and snow will find a way into the gas tank, especially if the fuel cap is loose or deteriorated. Even if equipment is inside, if you leave pump gas in the tank, your 10% ethanol fuel will attract water from the atmosphere. Most of the time this small amount of water will simply be burned off as the engine runs. Bear in mind that gasoline is less dense than water, so the water is always at the bottom of the fuel tank. Also keep in mind that a lot of, maybe most, mowers and snowblowers do not have fuel pumps and are gravity-fed. So the stuff at the bottom of the tank is the first to be burned. Yeah, I know that tanks are designed so the outlet is not at the absolute bottom so as to keep dirt, grass, leaves, and water from being sent to the carb. But if there is just enough water in the tank to get into the outlet, it will go first. A little water being combusted will not harm an engine. It will turn to steam and exhaust with the rest of the gases. So no worries about a few drops of rain or snowflakes. But if your carburetor bowl is full of water and stale gas because you left ethanol pump gas in the tank all winter, no amount of Seafoam or other alchemy will make the engine run.

Personally, when I put a machine into storage I run the tank dry and take the bowl off the carb and clean it out. Have done this since I bought my first gas powered mower, except the first year. Learned my lesson in year 2. I also drain the oil while the engine is still hot, and tape a note to the top of the engine saying, “No oil, you idiot!” Has worked so far, but no telling what foolishness I can find a way to wreak on myself.
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Why do you store with no oil vs adding the new oil right away?
 
l008com said:
Why do you store with no oil vs adding the new oil right away?
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This could be completely bogus but I once read that oil goes bad with time even if you aren’t putting miles or time on the engine. I don’t think a few months make much difference anyway, but I figure why not start the season with completely fresh oil?
 
I guess. In my case the oil i would be putting in the motor would just be sitting in the coil container for that exact same amount of time. In my mind, more oil in the crankcase means less exposed metal in the crankcase. *shrug*
 
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