How to quickly get rid of some old gas?
May 9, 2014 8:19 AM   Subscribe

I have one of those cherry red gasoline jugs that I use to store gas for my lawnmower. Usually I just re-use the gas from year to year, but I know that's bad (OLD GAS!), and I'm trying to take better care of my mower and do things like use new gas and change the oil and, you know, stuff, so I'd like to get rid of it and get some new gas...

There's about half gallon left in the container.

I can...

A) Go and get an appropriate disposable container and dump it into this container and then drive out to my local county-operated toxic chemical disposal center and pay money and drop it off and lah-dee-dah. I will do this. I'm not about to do anything sketchy with it, like dump it in the flower patch or something, but it sounds like a pain in the ass.

B) I have a 2014 Ford Focus. I have had several people suggest that if it has even a mildly full tank of gas, I can take this half gallon of old gasoline and just dump it in and my car won't bat an eye. This sounds way more convenient, but I don't want to wreck my new car over this.. It's supremely not worth it. However, the idea of being able to dump this crap without ever leaving my garage is supremely attractive.

So, the question is, I guess, how bad is old gas? In the scheme of things, in a modern car, is a half gallon of year old gas really going to be an issue? Can I come back here and yell at you if my car explodes? What do you think?
posted by kbanas to Science & Nature (12 answers total)
To get rid of it in a responsible manner, you might be able to take it to the place where you get your oil changed. They should be able to put it in with their waste oil (I think). Walk in with your gas can, they pour it out, hand your empty can back (probably).

One thing you can do to keep your gas in okay condition over the off-season is put a fuel stabilizer in it. I put fuel stabilizer like Sea Foam or whatever the auto parts place has in all the cans I use for lawn care equipment.
posted by randomkeystrike at 8:23 AM on May 9, 2014

how bad is old gas?

"Old gas" is kind of an urban myth anyway nowadays (in how it is presented by the sources I have seen). Year old fuel that has been stored correctly (in an airtight container) is no different to any significant degree to new stuff. If it is stored badly (and old, crappy fuel cells and inappropriate storage are largely the source of 'bad gas' stories) then it is a different story - if air gets to it it brings moisture and impurities and THAT is the bad stuff. The fuel itself doesn't degrade to any significant degree. There just isn't the same level of impurity in the fuel that is sold these days compared to years ago. The quality improvement means the degradation over time is nowhere near as pronounced if stored correctly.

if it has even a mildly full tank of gas, I can take this half gallon of old gasoline and just dump it in and my car won't bat an eye.

This is the case. Throw it in the car (especially if it is only half a gallon) and it won't matter at all.

Personally, if you'll use that much fuel before the year end, I'd fill the container up with new fuel (so a 50/50 split new for old) and just use it in the mower. As long as you refill it only when it is completely empty, all the old fuel is gone before the end of the season.
posted by Brockles at 8:40 AM on May 9, 2014 [1 favorite]

Just use it. It'll be fine.
posted by valkyryn at 8:46 AM on May 9, 2014 [1 favorite]

We use year old gas every year. The lawnmower, leaf blower, pressure washer and chainsaw don't mind at all. If it bothers you, just mix with new gas in the car, put the container in the back of it and use the old gas to drive and get new gas.
posted by Leenie at 8:56 AM on May 9, 2014 [1 favorite]

I had to get rid of some bad gas recently, but only because it had sat unused for a year and a half and my engine wouldn't start on it (refilled with fresh, and she fired right up). I couldn't find any "easy" places to take it (yeah, there's lots of places that take oil or other fluids, but nobody wants gas), so it had to go to household hazardous waste. I'm surprised you have to pay a fee for that, though. You might want to check again...I've never heard of a HHW collection that wasn't free.
posted by gueneverey at 9:13 AM on May 9, 2014

You're SUPPOSED to put Sta-Bil in it before the end of the season, but I never do anymore, and I've never had an old-gas-related problem with my mower, snow blower, et cetera.

When I had a motorcycle, I threw Sta-Bil in the tank before putting it away for the winter. I'm not sure if that was strictly necessary.
posted by tckma at 9:29 AM on May 9, 2014

I see from your profile that you're in Ann Arbor.

A quick Google search for "Ann Arbor hazardous waste" brought up the Washtenaw County Hazardous Waste Collection Program,

...which is free for county residents, and

accepts "automotive fluids" such as gasoline, so I see no reason why you would be unable to bring your old gas there.

You should be able to bring your old gas there, and they should take it, free of charge if you prove county residency.
posted by tckma at 9:35 AM on May 9, 2014 [2 favorites]

Oxidation is, AFAIK, the main threat to gas left to sit around. Oxidation turns it into gooey varnish. A sealed gas can has a limited amount of oxygen in there, and what's there has probably oxidized some gas. I suspect half a gallon of gas is probably not too badly harmed by the available oxygen in a few gallons of air.

Take Dr. Bronner's advice: DILUTE! DILUTE! OK! Add more gas to the can, and show your lawn who's boss. This will be a less-than-great, but still entirely adequate, can's-worth of gas. Just use it until empty before refilling.
posted by Sunburnt at 9:39 AM on May 9, 2014

I had a few gallons I drained from a generator before putting it into storage... the yard maintenance crew working next door were tickled to get it even after full disclosure.
posted by tinker at 10:14 AM on May 9, 2014

I routinely pour the leftover gas after mowing season into our Honda Odyssey tank so that I can start the season with fresh gas in the mower. Hasn't caused any problems whatsoever.

(Ok, so I haven't had much left in past years - a half gallon sounds right. Oh, and potential problem - if you're obsessive about calculating your mileage, this will screw up the calculation I guess.)
posted by RedOrGreen at 3:47 PM on May 9, 2014

Gas is ~8 pounds to the gallon (6.1 pounds to the US Gallon) so it's easy to determine how much gas you added to your tank with an accurate kitchen or bathroom scale.
posted by Mitheral at 11:30 PM on May 9, 2014

Yeah, mix it with good gas, you'll be fine whether it's in your car or the lawnmower. I'd probably put it in the lawnmower, because newer cars, especially flexfuel cars, have sensors that determine what fuel is in it and your mixed-up fuel might mess up your computer's settings.
posted by AzraelBrown at 8:00 AM on May 11, 2014

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