Will two-stroke fuel ruin my lawnmower?
February 29, 2008 3:31 PM   Subscribe

What would happen if I put gasoline with two-stroke oil in it into my conventional four-stroke lawnmower?

A while back, I borrowed a roto-tiller with a two-stroke engine. To fuel it, I mixed in a little bottle of two-stroke oil with gasoline a plastic gas can I had in the garage, the lid to which I lost a long time ago.

I tilled my rotos, and I've since given the roto-tiller back to its owner, who lives a considerable distance away and whom I don't often see.

I still have about a gallon and a half of gas/oil mix left over, in a container that has a piece of tinfoil and a rubber band for a lid, and I don't know what to do with it. Obviously I can't just dump it down the storm sewer, and I can't keep it in the garage because the can isn't airtight, so the garage fills up with fumes.

So I was thinking I'd just use it to run my lawnmower, a well-used cheapo Sears push mower with a Briggs & Stratton engine. What will the result be? A fouled plug? Nothing? A huge explosion?

Barring using this gas - which has an estimated value of $5.50 and would likely serve a summer's worth of lawn-mowing - how else could I properly dispose of it?
posted by M.C. Lo-Carb! to Home & Garden (13 answers total)
find someone with a two stroke lawnmower, boat motor, motorcycle, and give it to them..

don't run it in your lawn mower, it isn't worth the potential plug fouling and carb problems....
posted by HuronBob at 3:34 PM on February 29, 2008

and..if by "a while back" you mean 6 months or a year, don't use it in anything, take it to the nearest gas station and ask them to dispose of it for you...
posted by HuronBob at 3:35 PM on February 29, 2008

By a "while back," I meant last month.
posted by M.C. Lo-Carb! at 3:37 PM on February 29, 2008

It'll probably produce a little smoke. If you can't get rid of it at the gas station, it might be better to dump it in your car with a nearly full tank as that will dilute the oil more. But just getting rid of it is the best option.
posted by chairface at 3:39 PM on February 29, 2008

posted by Espoo2 at 3:44 PM on February 29, 2008


That's secretly what I was hoping for...

I guess I'll take it to a gas station. And they'll probably just dump it down the drain!
posted by M.C. Lo-Carb! at 3:50 PM on February 29, 2008

Your profile says you're in the ABQ -- you could also take it to the Bernalillo County Hazardous Waste Collection Center. The county household haz waste facility near me takes this sort of stuff all the time -- just label it and bring it over.
posted by harkin banks at 4:16 PM on February 29, 2008

It'll run fine in your lawnmower. If you run it at as little as possible at idle, then you may not even foul the plug. It'll also go fine in your (petrol) car (finish off a full tank with it, though). That's the two things I'd do with it. There is no earthly reason to throw it out or 'dispose of it' just because it has a little oil in it. What do you think petrol is made from!

Throw it in the mower. If you mixed it properly (ie not over oiled it) it'll be fine, but smokey. Old engines burn oil anyway, when they get worn out. It's no big deal at all. It is exceedingly unlikely you will foul the carb, if you foul the plug, then big deal, just take it out and clean it and carry on until it fouls again.
posted by Brockles at 4:45 PM on February 29, 2008

Ditto just use it in your car. The 50:1 ratio of one gallon of gas won't hurt a thing. In fact it could help by adding a little bit of top end lubrication.
posted by Gungho at 5:00 PM on February 29, 2008

I agree with burning it in the mower, but would just do it a little at a time, alternating tanks of regular gas with tanks of half oil-gas and regular gas. Here is some more discussion on the subject.
posted by TedW at 5:35 PM on February 29, 2008

I've burned tons of premix in my car over the years when I didn't feel good about putting it in my race bike anymore (no longer fresh). You'd never notice a thing. It will burn just fine in your lawn mower, too. I seriously doubt it would foul the plug, but you could dilute it further with straight gas if you wanted to be sure. I agree with Gungho that 50:1 won't hurt a thing. I've run 32:1 without incident for years.
posted by SciGuy at 8:09 PM on February 29, 2008

Smoke, lots of smoke. I've observed this experiment.

My sister decided to mow her lawn. Her mower needed gas. She had one gas can. It had liquid in it, so she put it in the fuel tank of the mower. She then ran around wondering why her mower was spewing smoke out of the exhaust. Her fiance had mixed oil and gas for the string trimmer.

A year later, the mower still works. I could imagine that doing this repeatedly would foul the plugs, but this one time addition had no ill effect, other than making the neighbors think we'd started a forest fire. YMMV.
posted by solotoro at 9:32 PM on February 29, 2008

It will be fine. The 50:1 mix that most modern 2 strokes use is a pretty thin mixture. Usually when people put their old premix into a 4 stroke and it smokes is because the gas is old, and the more volatile components of the gasoline have evaporated away leaving the oiler, smokier components. If it doesn't foul the plug in a 2 stroke, it won't foul the plug in a 4 stroke.
posted by gjc at 11:30 PM on February 29, 2008

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