Posts: 251
Joined: 10/30/2013
Location: Oceanside, CA USA
I have been told not to use premixed gas that is over 2 weeks old. The problem is I usually only get out once or twice a month, so I always have leftover gas that is "bad". I live in California and can't find a place that takes old gas. ...and I am not too excited about putting it in my truck or boat like a few of my friends have suggested.
What do you all do with yours?
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Joined: 4/15/2018
Location: TN, USA
First off, two weeks is a pretty small window. As long as it is sealed up between uses I wouldn't have a problem using it well after a two week window.
If I do get to the point where I feel it is too old to use in my bike I use it in my gas blower and weed eater, I just love the smell of it and it gives me a fix when I can't ride.
2018 KX450F
2005 KX250
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Location: Paducah, KY USA
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Joined: 1/31/2018
Location: Mansfield, OH USA
You can use 2 week old gas. If its a month, no.
If you want to get rid of it, put it in your car or lawn mower. Nothing wrong with that.
Posts: 251
Joined: 10/30/2013
Location: Oceanside, CA USA
So it is OK in the car because you are mixing it with 20 gallons of straight gas, right? ...I just cringe at putting something that is not good enough for my old motorcycles into my new truck.
The lawnmower idea sounds great, but I use less than 2 gallons a year in my mower.
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Joined: 1/31/2018
Location: Mansfield, OH USA
No its fine to dump in a truck. My f150 has a 26 gallon tank. Mixing a gallon of 2 week old premix is not even a concern.
I run 2 week old gas in my bikes all the time. Never an issue. I wouldnt even worry about it.
Posts: 824
Joined: 3/29/2016
Location: Ithaca, NY USA
Edited Date/Time:
Putting premix in a modern vehicle is a great way to ruin the catalyst. I've done it on old junkers but wouldn't do it on my new truck.
Throw it in the lawnmower or snow blower
Also, I've run 2 month old premix with no problems at all. I cut with some fresh fuel if I'm worried Give it a sniff and make sure it doesn't smell sweet before though.
Posts: 247
Joined: 1/24/2018
Location: Fuquay Varina, NC USA
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Your truck with massive auto engine doesnt require half the quality of fuel as your small engine dirt bike. Of course, that's probably slightly exaggerated but putting that gas in your truck will not have any sort of negative effect on it. At a month old, it's still probably equivalent to the garbage pumped into your car on a regular basis... just my .02
Posts: 315
Joined: 6/2/2014
Location: Paducah, KY USA
It will not hurt your truck at all. I wouldn't dump it in an empty tank, but it won't hurt anything. I had my ASE Master before I changed careers. I still work on cars if that makes you feel better about it.
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Joined: 3/29/2016
Location: Ithaca, NY USA
I also had my ASE master before switching to automotive engineering. Catalytic converters are poisoned by oil. I'd rather throw away $10 worth of gas than get hit with a $1-2000 cat efficiency code.
You won't instantly see the effects, but poisoning cumulates over time and will shorten the life of the twc
Posts: 315
Joined: 6/2/2014
Location: Paducah, KY USA
If you believe that, that is fine. But 6-8 oz of oil every now and then in 20+ gallons of gas will not hurt a converter. The flash point of pre mix is low enough that the converter will burn it off if the combustion doesn't. Do you understand how two stroke lubrication works? It isn't lubricating the combustion chamber, that gets burnt. Same with a car engine, it will burn that small amount of oil. No different than GM truck engines the last several years. The DOD engines all burn oil with a few miles on them. I have rarely had to replace the converter because of that. And some have been burning up to a quart per tank of gas.
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Location: CAN
2 weeks? I've used mix well over a month of sitting in a can... After that the rest goes to the lawnmower, pressure washer, pickup, etc...
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Location: So Cal, CA USA
I throw old gas in my truck. Little extra lubrication and it smells great 
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Joined: 3/29/2016
Location: Ithaca, NY USA
Agreed, except 2 stroke racing oil additive packages are much different than automotive oils. I do agree that a few oz mixed in to a full tank won't poison it in one shot, but it will shorten life.
A good example of this is this student competition, called SAE clean snowmobile challenge - teams try to reduce sled emissions without killing the power. A few teams have stuck with 2 strokes, and had added a catalyst, and even work directly with washcoat suppliers on their designs. Granted, it's not exactly an OEM level effort, but so far they've had to resort to having the catalyst be a servicable item due to oil poisoning. This is even with a modern ETEC gdi with oil injection to prevent over-oiling.
Posts: 251
Joined: 10/30/2013
Location: Oceanside, CA USA
Edited Date/Time:
If I could month old gas, my problem would be solved. Does the oil break down after mixed or is the problem that some gas evaporates through the plastic container and your mix is richer after a few weeks?
I use Maxima Super M btw.
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Joined: 1/31/2018
Location: Mansfield, OH USA
a few oz of oil spread out over 20+ gallons of gas isnt going to hurt anything. Youre making it sound like hes going to ruin his exhaust if he dumps premix in it. Its not true. Tons and tons of people do it, ive done it for years. This is the first time ive ever heard of something like this. I could see dumping straight oil into the cat ruining it, but not the miniscule amount we are talking about.
What do i know tho, im not a mechanic.
Posts: 1908
Joined: 6/3/2018
Location: Bennett, CO USA
Where is this 2 week study and results that show it going bad?
Store it in a metal can, off the ground or buy just what you need. Dumping it into a car or truck doesn't hurt a thing, very diluted at that point.
vomiting equals disqualification.
Posts: 251
Joined: 10/30/2013
Location: Oceanside, CA USA
The two week thing...No study, just the guys at the track. The guy who built my motor said something similar. I think I will just get a metal can and not have to worry about it. I rarely go more than a month between rides.
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Joined: 8/20/2015
Location: USA
It is petrol and oil. It does not go "old" that easy. There are bigger variations between summer and winter petrol then you will have from a few weeks or even month of storage in a bike or sealed container. 6 month no problem, 1 year maybe you would notice.
Sure, the fuel is not the same after a year or two, but, in 9 out of 10 cases you wont notice any difference. Again, there is big variations in petrol between the ones produced during summer vs winter which is similar to the effect storing has to petrol.
Posts: 1908
Joined: 6/3/2018
Location: Bennett, CO USA
Wasn't picking on ya mate, I have just seen this repeated constantly to the point where people think it is factual. Get that metal can can, keep it off the floor and in a cool, dry place. Will last a long time. If really worried use some Startron or similar product.
vomiting equals disqualification.
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Location: AL, USA
Posts: 251
Joined: 10/30/2013
Location: Oceanside, CA USA
No offense taken BR8ES. I appreciate the help. Going to get a metal can and ride more often. Problem solved.
Thanks everyone!
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Location: Snohomish, WA USA
I’m guessing premix with pump gas might be ok in your truck, but remember that things like C12 or VP110 are leaded, which I believe will ruins the converter and/or O2 sensors.
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Location: NY, USA
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Location: Paducah, KY USA
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I wouldn't worry about dumping fuel if you are riding once a month. I have used fuel that has been mixed for over a month and have never had a problem on my yz 250's. My engines are stock though, if yours has had work done you may want to follow the advice of your tuner.
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Joined: 2/2/2017
Location: Atlanta, GA USA
Posts: 265
Joined: 2/2/2017
Location: Atlanta, GA USA
I used to dump old pre-mixed gas in my ‘91 Tacoma all the time with no issues. The first time I put some in my ‘99 Tacoma the check engine light came on within a couple hundred miles. I had to have a sensor replaced. Maybe it was a coincidence, but I never did it again.
Posts: 422
Joined: 10/28/2010
Location: San Diego, CA USA
I have always stored my gas (mixed and straight) in a metal can. I also use a fuel stabilizer added to the gas. It will keep just fine like this for months! Don't let it set directly on a concrete floor - it can cause moisture to collect in the fuel. If you have to set it on concrete, get a piece of plywood to put below the can/jug .
