Lawn Mower Residual Gas Question

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Hello:
Thinking ahead a bit, but thought I'd ask now while I remember to do so.
Just bought a new Toro walk behind type of lawnmower.
Is it still a good idea to remove all (I guess there would always be a little left in the carburetor) of the gas from the mower by running it dry for the winter ?
Or, just leave what's in it, in it ?
Or, just leave what's in in, in it, but add some fuel stabilizer ?
Thanks, Bob
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Since it's a new mower, why not read the manual and see what the manufacturer recommends. Don't you think they are a better source than random internet opinions?
It's never OK to just leave the gas in it. It should be either drained/run dry or else have stabilizer added. The pluses for those that favor stabilizer is it's easier and reduces the chance that any carb seals will shrink.
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snipped-for-privacy@optonline.net wrote:

Hi, I Live in Calgary where the winter weather is severe. I never empty fuel tank on my mower(John Deere), snow blower(Toro), weed eater(Echo), chain saw(Stihl), etc. Never had trouble starting in the spring, never experienced other trouble. I keep them all in tool shed. Tony
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wrote:

I live in Las Vegas where it's 120 in the shade. And probably 160 surface temperature of a lawnmower in the sun.
One size does not fit all. Some people should never wear spandex. What goes for Canada don't work in the middle of the Mojave desert.
HTH.
Steve
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wrote:

trouble
Shouldn't be trying to grow grass in Vegas anyhow :-)
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wrote:

I know someone who left gas in their generator for two years and was unable to get started when the next outage came. Yeh, you might get lucky and have no problems, but it is hardly worth the trouble.
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wrote:

trouble
unable
Leaving it in for two summers is considerably different than one winder in Calgary. Even in the Denver area I don't usually bother with the mower for the winter. But, I would not even think of letting any engine sit for the summer with gas in it. Even with stabilizer. I have a generator but always store it empty.
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wrote:

than
fuel
the
for
always
And I forgot to add stabilizer won't help much with the long term anyway. The gas will evaporate after two years.
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On Sun, 24 Apr 2005 09:18:28 -0400, Robert11 wrote:

I have always added some stabilizer, and filled the tank up all the way. A full tank doesn't allow condensation (water) in the tank, which will happen if there is air space in there. Been doing this for years, on many different mowers (and other gadgets/vehicles), and never had a single gas-related problem.
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Robert11 wrote:

That's what I do, also this same subject was discussed for 2 days last week. Look for "Re: B&S Engine Off-season Storage: drain gas tank or stabilize?"
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I took my Honda to the shop because it wouldn't run. I know about engines, and couldn't make it run. The guy told me NOT to leave the gas in there for any length of time, or it changes completely, and is not very combustible.
I now either empty it out, or let it run dry before stowing.
Steve
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SteveB wrote:
...

I don't think you will go wrong empting it out, but your Honda rep is wrong, at least partly wrong. It takes considerable time for gas to go bad. It is a standard chemical reaction that starts slow and builds speed using free radicals in the process. Stabilizer just controls the free radicals. However there is a different reaction that can cause gas to go bad in a short time. If it is allowed to evaporate (and some older mowers did allow a lot of this) then it would go bad quickly from the evaporation of the liter components (stabilizer will not help this at all).
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wrote in message

I have had my Troy-Bilt 30 inch walk-behind for about 9 years and have never burned anything in it but Amoco (now BP) ultimate gasoline. For those unfamiliar this gas is as clear as a glass of water. I never drain, I never treat, and I never pull more than once (possibly twice the first time in the spring). I figure this costs me an extra 5 or 6 bucks a year over regular unleaded.
I acknowledge that this is purely anecdotal, but I figure that the stuff that turns to gunk is the stuff that is not refined out of normal gas.
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Rick Brandt wrote:

The stuff that turns to gunk IS normal gas. :-)
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Indeed.
Gasoline isn't a "pure" chemical. It's a mixture of hydrocarbons of various weights. Traces as light as propane or even methane, with traces as heavy as asphalt. Refining is nothing more than forcing the average to be roughly equivalent to somewhere around C7H16 or C8H18, reducing the "tails" of the distribution to a "reasonable" level and specified octane level, and having enough "lights" to give you enough vapor pressure.
Evaporation acts almost as "fractional distillation". The light parts evaporate preferentially, leaving the heavy/sticky parts behind.
Which means that "gumming up your carb" is not necessarily (or even largely) a chemical process, but is in fact a physical one.
With small engines (especially weed wackers and the like), running the motor dry and then putting it away is the worst possible thing you can do. The residue gas solidifies in place. If it's 2-stroke mixed gas, it's worse because the mixed oil is going to congeal and evaporate into a sticky obstructive mess.
Think of gasoline like corn or maple syrup. Sticky to begin with, it gets vastly worse if the water is allowed to evaporate.
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Chris Lewis wrote:

Gasoline not only suffers from evaporation as you well explained, but it also suffers from chemical reactions that can occur without any evaporation. The various hydrocarbons can and do tend to react among themselves, generally forming heaver - longer chains. This is the part of the process that stabilizers can help slow down. This part of the process generally takes a fairly long time.
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True enough, but with 2-cycle gas, it implies that even a stabilizer won't help (much) if you encourage evaporation (ie: running the engine dry). Stabilizer or not, the majority of the gasoline residue will evaporate, leaving the heavy ends and 2-stroke oil behind. Gasoline stabilizer cannot prevent that from turning into sticky/obstructive goo.
Particularly nasty in engines with small fuel lines and small fuel passages in their carbs (ie: weed wackers).
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but the theory is that if you let it run dry, there is only a small amount of gas left in the carb, yes that will evaporate and leave a small amount of residue...
the alternative is leave the tank full and you then have an unlimited amount of gas to evaporate leaving a much larger amount of residue...
thats why I add Stabil then let it run dry. whatever small amount of gas is left still prbobaly evaporates but if there should be a large pool left somplace, the Stabil will slow down the degredation.
If the object of the game is to have the least amount of residue left, my bet is to have the least amount of gas avaialbe (i.e let it run drey) and have the gas that is left, stabilized. i.e. put stabil in before I let it run dry.
Mark
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I think putting in the Stabil is a waste of time. If you drain the tank and then run the engine until it dies there isn't enough left to leave any residue. There is no place to leave a "pool" at that point.
As others have pointed out in cool climates I have found no problem. When I lived in a warm climate I found reasons to start the mower occasionally so it was still not a problem. In cold climates the snow blower is the most likely to gum up if you don't drain the tank. I have been doing that for 30 years and that same engine still starts on the first pull each winter. I also use Mobil 1 5W30 oil in it. Never have drained or added to my lawn mower and it is on it's 25th year. Still starts on the first pull. But it is stored in a rather cold area that rarely gets much above freezing. The blower on the other hand experiences 90+ for months.
I guess the bottom line is to do whatever you feel safe with.
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Mixed 2-stroke gas is fairly viscous, and there'll be considerable residual gas, of which anywhere up to 1/16th of it is goo-forming oil.
Then, with small bore lines and carbs (ie: weed wackers), you could have gunkification within a few weeks. Especially on things like in-tank fuel filters where the elements will be saturated with gas no matter what you do in turns of running dry. Come spring, the elements are plugged.

It takes a very long time even for a (sealed) weed wacker tank to appreciably evaporate. Meanwhile, the volatiles are keeping the fuel from sludging up (and stabil would prolong that).

Stabil will not slow down evaporation. Once it's evaporated leaving two-stroke oil behind, stabil won't prevent it from becoming sticky muck.
On the last weedwacking day of the season, I simply stop my stihl and hang it on the wall. Full of gas. Come spring, it starts in 2 pulls. Just like it does in the summer when used every week.
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