The Smart Aleck answer is, "You put it there."
When you pour oil in via the fill hole, you're pouring it directly into the crankcase of the engine. I believe most simple, single cylinder, 4-cycle lawn mower engines are "splash systems". In which case, it's up to mechanical agitation to splash the oil around while the engine is running, ensuring that the valve components and cylinder walls are lubricated.
depending on what type of mower and who makes the motor it can vary. if it is a standard push mower you can either remove the dip stick/oil fill and dump the oil out there or look at the base of the motor for a plug or under the deck with the blade for a plug. if it is a riding mower there will be a plug at the base of the motor that can be removed to drain it
regular 10w 30 motor oil
If it is a 4-cycle engine you definitely need motor oil. If its a 2-cycle engine then the oil is mixed with the gas. If its a reel mower then no oil is needed except for external lubrication. Depending on the engine manufacturer the 4-cycle engines will require either SAE30 or 10w30 motor oil.
regular 10w 30 motor oil
some times there on the bottom of the motor, and some times there on the side of motor by the base, if you have a Push mower then it,s likey to be under the deck side at the bottom of the motor,
No, you should not use bar and chain oil as a substitute for motor oil in a lawn mower. Bar and chain oil is specifically formulated for use in chainsaws and is designed to adhere to metal surfaces under high pressure and temperature, while motor oil is formulated to lubricate engines. Using the wrong type of oil can lead to improper lubrication, increased wear, and potential engine damage. Always refer to your lawn mower's manual for the recommended oil type.
Just a standard 20/30 weight motor oil.
If its got a oil plug its a 4 cycle, 5w-30 motor oil
I don't think you need to. There is no motor, so it doesn't need oil.
Usually no difference except that later model vehicles require a multi-viscosity oil (5w-30, 10w-30. etc) while the regular 30w is recommended for small engines such as a lawn mower.
You will burn the motor up, which will be a very costly repair.
Yes, that is the correct weight.