If you are tight on storage space or just want the lawn mower out of the way, it may be tempting to store it vertically. However, the typical gas-powered lawn mower should not be stored vertically. A vertically stored lawn mower can leak gas and oil.
Additionally, even if it does not leak outside of the engine, it can excessively drain into the wrong areas of the engine. This can cause problems for the mower such as difficulty starting the engine, a locked up crankshaft, and potential damage.
However, there are gas-powered lawn mowers that are designed to be able to be stored vertically. An example of this type of lawn mower is the Toro SmartStow, which is designed to prevent leaks when stored upright. The company claims that vertical storage of this mower reduces the storage footprint up to 70 percent.
There are also electric/battery-powered lawn mowers that can be stored vertically due to their lack of oil and gas. The Snapper XD is an example of an electric lawn mower that is capable of vertical storage.
However, keep in mind that not all electric/battery-operated mowers are designed to be stored vertically. For example, the manufacturer of a GreenWorks 20-inch corded mower indicates that their mower is not designed for vertical storage due to it being unbalanced in this position.
In conclusion, we would not advise to store a lawn mower vertically unless the manufacturer specifically indicates that this is an option. Check the owner’s manual or the manufacturer’s website if you are unsure if a mower can be safely stored vertically. You can also email or call if these sources are unclear.