Just picked up my new grass mower. Got it home put it to gather. Looks great. Has a BRIGG & STRATTON motor. Guess what the dumb ass people at BRIGGS did leaves out the oil plug. O yes you have to turn it up side down to change the oil. REAL smart. I took the crap back and got my money.
The oil is mean't to be drained through the dipstick tube. Simply pull the dip stick out and tilt the unit on it's side, the oil will drain nicely into a pan. It's much easier to remove the dipstick than a stuck oil drain plug. Also no need to scrape the bottom off to find the drain plug.
Another reason I like it is it's easier to have the drain pan next to the unit instead of trying to shoe horn it under the deck.
I have this feature on my mower and it works great. I suspect if you would have read the opertaors manual it would explained this.