[Troutner]

Lawnmowers and other lawn equipment, such as tillers, have similar motors. However, most large yard machines use a four-cycle engine designed to work for prolonged periods. Smaller machines, trimmers and chain saws, have a lighter, more powerful two-cycle engine to provide a burst of high-speed power; these motors require a mixture of gas and oil to run, while four-cycle engines have separate tanks for gas and oil. However, getting oil in the gas will not permanently damage the machine.

[citizen]

If you have a problem draining the oil by tilting the lawnmower, you can remove the oil tank and invert it over a container or an oil-absorbent pad to catch the oil. Once the oil drains, mix some dishwashing liquid that contains a degreaser with warm water, pour it into the tank and swish it around to remove any oil clinging to the tank sides. Dry the tank using a can of compressed air. Replace the tank and fill with gas before mowing. here

[suckless]

On a four-cycle lawnmower engine, the oil and gas go into separate areas of the motor. If you accidentally pour oil into the gas tank, it will not damage the mower if you drain it and replace it with gas. Maneuver the mower so that the oil can drain from the gas tank and get as much out as possible. Put the oil in its proper place and use the mower as usual. Any oil left in the gas tank burns through the exhaust, so it may be smoky until it burns off. more

[abstraction]

Ideally you want absolutely all the liquid from the oil tank to be drained.

[bernardkatz12]

Oil serves as a lubricant in most machinery, so by running your lawn mower with gasoline (which is much thinner and a solvent) instead of oil, it is possible that the gasoline was not allowing the engine to be properly lubricated, which could lead to extensive damage to engine parts like the crank bearings, pistons and piston rings, cam bearings, motor, and other parts. [links]

[LuciferUA]

As soon as you realize that there is gas in the oil tank instead of oil, immediately shut off the engine. Do not attempt to start the engine until you have completed all the necessary steps to make sure that the lawnmower is safe to be used again.

[kenjo]

Wipe away any grass or other debris from your oil drain plug. Use a wet cloth and some elbow grease to remove tough, stuck-on debris. On most mowers, the oil drain plug is below the deck. Wiping debris away from the drain plug helps protect your crankcase from becoming contaminated.

[Bloof]

Screwdriver or allen wrench/hex key [links]

[Mike Hearn]

Like your car, your lawnmower needs gas and oil to run properly throughout its life. Unlike your car, however, the gas and oil fill holes on lawnmowers are often much closer together. Pouring gas into the oil fill tank is an unfortunate mistake, but not one that is difficult to remedy. Draining and refilling the oil tank a couple of times will remove the diluted oil and allow you to get mowing before your grass gets out of control.

[pjwaffle]

Lawnmowers and other lawn equipment, such as tillers, have similar motors. However, most large yard machines use a four-cycle engine designed to work for prolonged periods. Smaller machines, trimmers and chain saws, have a lighter, more powerful two-cycle engine to provide a burst of high-speed power; these motors require a mixture of gas and oil to run, while four-cycle engines have separate tanks for gas and oil. However, getting oil in the gas will not permanently damage the machine.

[aaaxxx]

If you added oil to the gas tank and didn't realize it until you tried to start the engine, the oil is most likely in the fuel line and primer pump. In this case, remove and replace the fuel line. Once you replace the line, you can try to start the mower; if it won't start, spray some starter fluid into the engine carburetor and try starting again. [links]

[nphyx]

On a four-cycle lawnmower engine, the oil and gas go into separate areas of the motor. If you accidentally pour oil into the gas tank, it will not damage the mower if you drain it and replace it with gas. Maneuver the mower so that the oil can drain from the gas tank and get as much out as possible. Put the oil in its proper place and use the mower as usual. Any oil left in the gas tank burns through the exhaust, so it may be smoky until it burns off.