I believe there is a plug on the bottom of the motor (above the blade, under the deck) but the manual says to turn the mower upside down and drain the oil through the dipstick tube.
Seriously.
The best way to change the oil on a Craftsman Eager One lawn mower - 6.75 HP is to buy a Toro.
It should be located on the same side as the oil dipstick just down on the bottom of the block just above the deck. Should be a plastic plug about an 1" in diameter
Where is oil plug
The engine has a drain plug located on the engine block. Look closely and you will find it.
Your owner's manual should explain that.
Remove drain plug and allow oil to drain. Insert drain plug. Remove fill plug and fill with the appropriate type and amount of oil. Install fill plug.
youtube - push mower oil change.... oil plug under mower deck
1/2 an inch
The mower should hold about 1/2 a quart, 16 ounces of SAE-30 weight oil...this is based on draining the oil from the engine.
To change the oil on a Craftsman 6.5 hp log splitter you first need to drain the current oil. The drain plug is on the bottom of the engine crankcase. Once drained, replace the drain plug and fill with new oil via the dipstick tube.
The oil drain plug for the Craftsman 625 series lawnmower is located on the bottom of the mower, just above the blade. Tip the mower back. The plug is round and threaded with a square head. Using the square head of a ratchet extension, twist the plug counterclockwise and remove. The oil will start draining. Once it has drained, replace the plug and tighten clockwise until snug. Replace with new lawnmower oil or SAE-30 weight oil.
On a Briggs, right side, above the frame towards the rear of engine.