The crankshaft is spinning above the normal noil level. If the oil level is too high, the crankshaft can 'dip' into the oil, effectively acting like an eggbeater or blender. That causes the oil to be whipped up, incorporating air bubbles. You can tell if this has happened by looking at the dipstick, and seeing if the oil is whipped up. If air is incorporated into the oil, it doesn't have the same lubricating qualities, and you can experience major engine damage, including bearing and crankshaft failure.

Oil doesn't seep anywhere if it is overfilled, especially into the cylinders, as the cylinders are located above the oil level.

Thanks for the info. I've just finished draining some of the oil out from the bottom. What a messy job but thank god I was prepared for it!

I think I drained out quite a bit and now back to just below the upper mark.

I drove the car for about 50Km only after overloading it last night, then drained it out this morning. Should I have the car checked / serviced asap?

Depends on whether the oil looked like a milkshake or not. If not, I wouldn't worry about it.

I would think you would be fine since you caught it right away and made fixing it a priority.

Thanks guys.

Nope, didn't look like "milkshake" at all.... looked pretty normal except slightly darker than expected (suppose to be new oil).

I'm monitoring the oil level / quality and the fuel consumption closely. I was quite shock when the level went to so low only 3 months (4000km) after the oil service. I checked and couldn't find any obvious leak.