For some, mowing the lawn is more of a hobby that a labourious task. If you're one such person, the satisfaction that comes with a perfectly mowed lawn is sufficient payback for the labour you'll have put in.
You'll need to take perfect care of mowing equipment if you hope to reap the benefits of a perfect-looking lawn. Proper storage of mowing equipment not in use is an integral component of caring for lawn equipment. Contrary to what you may have heard, draining fuel from the mower before storage might prove to be more harmful than it is beneficial.
Gum And Varnish
You'll have to accept that it won't be possible to drain fuel from the tank to the last drop. Even with the most sophisticated of draining techniques, droplets of fuel are bound to remain along the walls of the tank.
An empty fuel tank provides sufficient space for the entry of atmospheric air into the tank. Oxygen in the air will react with fuel droplets inside the tank to form gum-like deposits and/or varnish. These deposits could easily end up being deposited along valves and fuel lines within the mower's engine. If gum/varnish deposits are left to accumulate, the clogging of fuel lines is an inevitable occurrence.
A drained fuel tank also provides sufficient space for the condensation of water vapour inside the tank. Presence of moisture/water inside the tank encourages corrosion and the development of rust on tank walls, along fuel lines and within the carburetor.
Corroded sections of the tank are weak points through which fuel could leak once it's time to put the mower back in operation. If the extent of corrosion is severe, you'll be forced to replace affected components of the mower's engine system before the equipment is ready for normal operation.
The Way Out
Instead of draining the fuel tank, you could simply add the relevant treatment (additive) to the fuel and drop the mower at the preferred storage location with the fuel still in it.
These treatments are chemical additives that suppress the undesirable properties of fuel, thereby preventing the kind of problems discussed above.
For example, deposit control additives (also known as detergents) create a protective film/barrier that deters the formation and accumulation of gum/varnish deposits. Additives that protect against corrosion (corrosion inhibitors) adhere to metal surfaces of the tank. Thus, they act as a protective barrier that prevents contact between the metal surfaces of the tank and agents of corrosion.
For more information, talk to a professional like MTA Australasia.