# How long is it safe to let gas sit in carb?



## barney (Nov 21, 2017)

About how long is it safe to allow non ethanol gas to sit in your carb between snow storms? 

Last time I used the machine was 4 weeks ago. Am thinking I better go start it up and let it run for awhile.

Actually bought the gas approx 80 days ago in total. I did put some Napa brand gas treatment in it at the time.


I know many guys recommend runnning the carb dry after each use and will start doing that I think. Last time I tried it I was kind of unnerved by how loudly and erratic the combustion bangs were and fearing engine damage quickly re-opened the fuel valve and then shut it down normally. :smile_big:


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## micah68kj (Oct 8, 2011)

I use non ethanol and never drain my tanks/carbs. Never have had any rust or starting problems. Before switching to E free gas I always used gasoline treated with Startron and Seafoam. No problems.. Many here will disagree but this works for me. "If it ain't broke don't fix it."
Note: I still use Startron in the E free gasoline, at least until I use up the two bottles I have.


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## UNDERTAKER (Dec 30, 2013)

*When you get done turn off the fuel valve and let the engine starve it self oot. as for the main tank itself it does not matter.*


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## Dannoman (Jan 16, 2018)

I find it's best to turn the fuel shut off valve to the off position while the machine is running so the fuel in the bowl gets consumed. Just remember to turn the valve back to the on position when you restart next time. A habit you will get used to.


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## sscotsman (Dec 8, 2010)

I use non-ethanol gas with seafoam, for all my mowers and snowblowers.

For the snowblower (1971 Ariens) it sits about 7 months in the off-season, March to October.
For annual Autumn prep (grease, oil, lube, oil change, etc) I drain the gas tank but *dont* mess with the carb.
Do all the maintenance..fill with fresh gas..fires up fine.
the only "old" gas is in the carb, quickly burned off and replaced with fresh gas.

For the mowers (1964 Wheel Horse tractor and 2006 Craftsman push mower) they sit about 5 months in the off-season, November to April.
For annual Spring prep (grease, oil, lube, oil change, etc) I drain the gas tank but *dont* mess with the carb.
Do all the maintenance..fill with fresh gas..fires up fine.
the only "old" gas is in the carb, quickly burned off and replaced with fresh gas.

I never actually empty the carbs..ever. 
Been working fine for 12 years now.

Scot


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## guyl (Jun 12, 2016)

I never empty the carb, shut off fuel or run it dry during the season. For summer storage, I leave the tank about half full, add stabilizer, and run it for about 5 minutes. Has worked for 40 years and counting.


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## GoBlowSnow (Sep 4, 2015)

I've let fuel with up to 10% ethanol in it sit in the tank and carb for up to a year and a half and have never had an issue. Sure it smelled bad when fired it up, but it still ran.


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## stromr (Jul 20, 2016)

I use non-ethanol gas and a stabilizer, whatever's on sale and don't drain or run dry anything. Only carb problems I have is when I buy a machine I don't know the history of. Once I've cleaned or replaced the carb, no problem everafter!


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## tpenfield (Feb 24, 2015)

I'd be concerned if it was over 3 months, but as the others have said, if you can run the carb dry by using the shut-off valve, that would be better.

Using fuel stabilizer also puts you in a better situation with layups.


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## FearlessFront (Aug 18, 2016)

Ethanol fuel has a shelf life of 90 days before it starts breaking down and causing problems. If you add stabil to the fuel it gives the fuel a shelf life of 2 years (24 month's). Always use stabil and if in doubt just turn the fuel shut off closed and run the machine dry, in case their is no more snow and you forget, this way your safe either way.


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## JLawrence08648 (Jan 15, 2017)

Briggs says do not use gas older than 3 weeks.


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## Jarsh (Jan 4, 2018)

Used stabilizer for 14 years in a Craftsman mower with Tecumseh engine. Never bled the carb nor has it ever been worked on. One to two pulls after priming. Never an issue. Been using Seafoam in my HSS622 and no starting issues thus far. Don't bleed the carb and I always store with a full tank of fuel.


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## aldfam4 (Dec 25, 2016)

micah68kj said:


> I use non ethanol and never drain my tanks/carbs. Never have had any rust or starting problems. Before switching to E free gas I always used gasoline treated with Startron and Seafoam. No problems.. Many here will disagree but this works for me. "If it ain't broke don't fix it."
> Note: I still use Startron in the E free gasoline, at least until I use up the two bottles I have.


I pretty much follow above regiment. I use E free gas, Seafoam and Stabil - 360 and for me this works. I do run my machines dry at the end of season.., I have had good luck with doing it!


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## Freddy Ford (Jan 30, 2018)

The general consensus is 30 days for E10 gas, which is what most of us have to suffer with. I envy those who have ethanol free gas availability, as most people don't have that option. Stabilize everything, even in the summer with mowers, etc. You will never have a problem. The large bottle of regular Stabil is cheap and effective, but their are lots of options today.


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## tadawson (Jan 3, 2018)

Well, this is reaching a bit, but thr question was 'how long is it *safe*', and not how old a fuel will run' . . . I recently restored an engine that sat with fuel in the carb between 15 and 20 years . . . no damage at all, but did need a cleaning. I guess that would be considered 'safe'. . . .

More realisticaally, sometime I forget to run my mower dry, and rarely have any trouble starting it afer 4 or 5 months . . . I do use stabilizer, though. The gas can typically goes a couple months between fills as well.

- Tim


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## crazzywolfie (Jun 2, 2014)

tadawson said:


> Well, this is reaching a bit, but thr question was 'how long is it *safe*', and not how old a fuel will run' . . . I recently restored an engine that sat with fuel in the carb between 15 and 20 years . . . no damage at all, but did need a cleaning. I guess that would be considered 'safe'. . . .
> 
> More realisticaally, sometime I forget to run my mower dry, and rarely have any trouble starting it afer 4 or 5 months . . . I do use stabilizer, though. The gas can typically goes a couple months between fills as well.
> 
> - Tim


the fuel was different 15-20 years ago tho. they didn't use ethanol mixed fuel like they do today. the ethanol reeks all sorts of havoc with carbs and aluminum. yes almost everything is cleanable but some people don't like having to go thru the inconvenient of tearing apart a carb to get thing running good again. 

personally i would go with what the manuals say if you have to run fuel with ethanol. 30 days. then dump it in the rest in your car and get a fresh tank for the snowblower. i do agree with the people who are saying to use the fuel shut off valve if your machine has one and running it dry every time. i never hurts to run the carb dry since that is what usually gets clogged up when you let fuel sit in it. fuel tanks and fuel lines are usually pretty easy to clean compared to a carb.


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## oldackonoak (Feb 11, 2018)

FearlessFront said:


> Ethanol fuel has a shelf life of 90 days before it starts breaking down and causing problems. If you add stabil to the fuel it gives the fuel a shelf life of 2 years (24 month's). Always use stabil and if in doubt just turn the fuel shut off closed and run the machine dry, in case their is no more snow and you forget, this way your safe either way.


This is a fact about Ethanol fuel. I don't have access to non ethanol fuel if I did I would run that. You can buy it at the dealers but it is to expensive. I don;t shut anything off when the machine is being used but when it comes to storage I add a stabilizer let it run for 10 min and shut off the fuel. As far as the type of stabilizer I have used many and never had bad results with any. Donnyboy73 has a cool video on a product called K100 I think just look up water in gas. He compared it with seafoam and it does actually mix the water and gas together so it would be combustible but that doesn't replace the stabilizer.


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## tadawson (Jan 3, 2018)

crazzywolfie said:


> the fuel was different 15-20 years ago tho. they didn't use ethanol mixed fuel like they do today. the ethanol reeks all sorts of havoc with carbs and aluminum. yes almost everything is cleanable but some people don't like having to go thru the inconvenient of tearing apart a carb to get thing running good again.
> 
> personally i would go with what the manuals say if you have to run fuel with ethanol. 30 days. then dump it in the rest in your car and get a fresh tank for the snowblower. i do agree with the people who are saying to use the fuel shut off valve if your machine has one and running it dry every time. i never hurts to run the carb dry since that is what usually gets clogged up when you let fuel sit in it. fuel tanks and fuel lines are usually pretty easy to clean compared to a carb.



Yeah, I wasn't recommending 15 years . . . :grin: But then again, I think 30 days is crazy short. The mower I mentioned (Honda) is from 1989, never needed cleaning, and often sees multi month old fuel from over the winter, without issue. On the mower (unlike the blowers) I am sadly hit or miss on draining it or running it dry. I do fuel up just prior to use, so rarely get full tank of old fuel . . .

(Note that this is just my experience, which may well amount to nothing in other environments, and I'm certainly not recommending it . . . just sharing an observation).


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## Tony P. (Jan 9, 2017)

While ethanol can cause serious problems from phase separation, ethanol-free gasoline can still cause problems due to *oxidation*, often called stale fuel. Gasoline (with ethanol or ethanol-free) is inherently unstable and that instability causes it to degrade soon after refining. Much of the degradation of gasoline is caused by oxidation. Stale fuel causes gum and varnish - sticky substances that cling to everything causing clogs and eventual failure to the carburetor and engine.

Oxidation has been around for as long as gasoline but is generally not a critical problem in sealed fuel systems, such as vehicles. However, today's small engine fuel systems are not sealed - their gas tanks are vented, as are many gas cans. As a result, oxidation can occur fairly quickly - beginning in as little as 30 days, particularly if the gas tank or can is kept less than half full.

Gasoline additives can control or diminish oxidation, which is why they should be used in all gasolines for small engines.

BTW, I'm not familiar with a NAPA brand additive.


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## dbert (Aug 25, 2013)

And...


> Ethanol attracts water. When the two get together, they create the perfect environment to grow a type of bacteria called acetobacter. *After getting drunk on their EPA-sponsored kegger in your gas tank, the acetobacter excrete acetic acid. And acetic acid is very corrosive.*
> 
> If you’re refilling your gas tank every week or two, acetobacter don’t have time to grow a sufficient size colony to damage metal parts in your fuel system. But if your fuel sits for longer periods of time these microorganisms continue to multiply until your gas tank contains damaging levels of acetic acid.


https://www.equipmentworld.com/e-10-alive-the-corrosive-damage-ethanol-gasoline-does-to-your-fuel-pump/


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## Tony P. (Jan 9, 2017)

dbert said:


> And...
> 
> https://www.equipmentworld.com/e-10-alive-the-corrosive-damage-ethanol-gasoline-does-to-your-fuel-pump/


I don't believe a meaningful connection has been made that gasoline + ethanol + bacteria = corrosion in small engines. While it's true Acetobacter produced corrosion in a laboratory setting around 10 years ago and there is a real possibility for very dirty industrial equipment to attract the bacteria, that seems to me to be a long way from definitively making this connection.

*To my knowledge Acetobacter has not been found inside engines or components and it would be good if someone would dispute that. I'm ready to stand corrected.*

I'm not saying ethanol phase separation can't lead to corrosion in small engines; only that that process has nothing to do with bacteria. 

Acetobacter is commonly used in fermentation (primarily vinegar) which is a long way from small engines.


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## crazzywolfie (Jun 2, 2014)

tadawson said:


> Yeah, I wasn't recommending 15 years . . . :grin: But then again, *I think 30 days is crazy short*. The mower I mentioned (Honda) is from 1989, never needed cleaning, and often sees multi month old fuel from over the winter, without issue. On the mower (unlike the blowers) I am sadly hit or miss on draining it or running it dry. I do fuel up just prior to use, so rarely get full tank of old fuel . . .
> 
> (Note that this is just my experience, which may well amount to nothing in other environments, and I'm certainly not recommending it . . . just sharing an observation).


 i am pretty sure that is what most manuals say. if you are not using it for more than 30 days to drain it. i could possibly see it being true. the smaller the amount of fuel the quicker the reaction happens especially when dealing with something the size of a float bowl. storage definitely has a huge effect on that too. storing a machine in a garage would help the fuel last longer than sitting out in the sun/weather all the time.

i personally spend the bit extra with my carbed engines and get the shell premium fuel which is luckily ethanol free around me. ever since the switch years ago it has saved me the yearly clean the carb out. i know i have even had a few people tell me the 2 stroke oil is suppose to help the fuel stay longer but my 2 strokes still had issues with the ethanol in the fuel.


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## HCBPH (Mar 8, 2011)

I ran into something new last night. I bought a machine for the engine and started tearing it down. It had about a half tank of gas in it, no big deal -right? I usually drain the tank and let it evaporate. Surprise Surprise - the fuel was blue like it had some brand of stabilizer in it. That wasn't the real surprise, there was ice in the tank. Not just a little, a lot. Unless they had water in the gas can, I've never seen anything like that before.

Just a comment.


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## broo (Dec 23, 2017)

For my part, I use non-ethanol 91 octane fuel with stabilizer and Marvel Mystery Oil (don't know if it helps or not, but I got a 6 pack of the stuff I have to somehow use). I have no fuel shutoff valve on any of my OPE and I don't drain the carbs since I don't know how. No problems yet with neither winter or summer equipment.

HCBPH, my guess about the blue fuel would be that someone used Stabil Marine in it. That stuff is blue.


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## barney (Nov 21, 2017)

Tony P. said:


> While ethanol can cause serious problems from phase separation, ethanol-free gasoline can still cause problems due to *oxidation*, often called stale fuel. Gasoline (with ethanol or ethanol-free) is inherently unstable and that instability causes it to degrade soon after refining. Much of the degradation of gasoline is caused by oxidation. Stale fuel causes gum and varnish - sticky substances that cling to everything causing clogs and eventual failure to the carburetor and engine.
> 
> Oxidation has been around for as long as gasoline but is generally not a critical problem in sealed fuel systems, such as vehicles. However, today's small engine fuel systems are not sealed - their gas tanks are vented, as are many gas cans. As a result, oxidation can occur fairly quickly - beginning in as little as 30 days, particularly if the gas tank or can is kept less than half full.
> 
> ...


Excellent info. Thank you. Maybe it wasn't a NAPA brand. It was a small bottle I bought at Napa.


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## jrcjr (Sep 23, 2017)

I didn't believe it myself, but here's pretty much the final word until someone suggests something else and different testing is done. (i.e. New hypothesis, new testing and observation, etc)

NIST - National Institute of Standards and Time (Kinda like the CDC or NIH, but for things that involve physics, chemistry, or other sciences that don't involve a human body.)

https://www.nist.gov/news-events/ne...s-suggest-need-underground-gas-tank-retrofits


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## sunlight99 (Sep 2, 2017)

Toro manual says to drain the fuel in the carburetor after running the engine dry, is that needed?


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## HCBPH (Mar 8, 2011)

sunlight99 said:


> Toro manual says to drain the fuel in the carburetor after running the engine dry, is that needed?


Can't hurt, particularly if you have a metal tank, don't treat your gas or use ethanol fuel. I think you'll find manufacturers will lean to the side of caution especially if there's a warranty involved.


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