Ok so I try to change the oil on my dad's '00 accord 4cyl for the first time. I stupidly didn't read the manual the first time and I found a drain bolt right under the filter and assumed this was it. However I only got like 100mL of oil from it. I later read the manual and found out the real drain bolt was at the very bottom and the bolt didn't take a drain socket, rather a standard hex. This was the correct bolt and I was able to properly drain all of the oil.

I'm wondering what that oil I originally drained was for? I didn't screw anything up did I?

I wouldn't drive it until you find out what exactly you drained. Someone will chime in pretty soon, princess might help if you send her a PM if no-one answers.

I've changed my 02's oil several times, but I have no idea about the bolt you found "right under the filter." Assuming you put both bolts back in correctly and checked your fluid levels you should be okay. I'd run my hand around that upper bolt again to make sure I had not caused a new leak.

Also note that the oil drain plug has a crush washer which should be replaced at each change. Some don't bother, but for 20 cents or so it's worth it.

Engine oil:
The oil drain plug is below the filter, but much farther down (closer to the ground), on the engine oil pan (black in color), near the bottom. Takes a 17mm box-wrench (a socket will work too). And you will need about 4-4.5 Quarts of 5W-20 oil. 10W-30 will results in about 1-2 MPG poorer fuel economy. Change every ~7,000 (7K) miles (When I was using conventional oil I did myn every 5K). Probably best to change the filter every time you change the oil.

Trany oil:
The one that take the square socket is for a 3/8 ratchet, this is the drain plug for the transmition (on the aluminum (silver) color metal), and it reacquires about 2-2.6 Quarts of Honda ATF (Z1), to refill it. Do not substitute any other ATF (there is no pan gasket or filter to change. Just drain and refill, every ~30,000 (30K) miles (I do myn every 15-20K)...

I'll take a pic tomorrow, it took a hex drain bolt, I guess about 3 inches below the filter, and oil came out. I tightened it back and everything seems fine.

If the bolt you took out was a 12mm head, (8 mm bolt) that's the maintenance bolt to lock the balance shaft while doing a timing belt.

A very small amount of oil comes out when it is removed. No damage was done as long as you put it back with it's sealing washer.

The engine drain plug as you found out is the 17mm head (14mm thread) bolt in the sheet metal pan.

Ah thanks for the info, I did put the bolt on tight again, glad it wasn't serious.

Should be like far left on the oil pan... As said its a 17mm head bolt...

Bolt should be put on about 17-20 Ft Lbs, Don't really crank on it, Hand tighten.

oops did 40ft lbs :P

oops did 40ft lbs :P

The owner's manual says 33 ft/lbs for the 99 which should be exactly what yours is set to but read the manual to be sure. I would leave it as it but be careful next time because you can strip it. I usually hand tighten it with a 3/8 ratchet and get it tight without going too much overboard. I bet it probably is less than what the manual calls for but have had no leaks in 6 years of changing it myself.