Hello I'm very new to motorcycle so this is probably a newbie question. Today I noticed the engine oil droped from a bit over half to the bottom on the oil gauge, after about 2 hour of riding. Maybe it's because I tends to ride at high RPM (4-6k) which caused this? On the owner's manual it says you might need to refill the oil more often if you ride it fast. I hope this is not caused by something mechanically wrong with my bike... BtW which engine oil should I buy? Any insights are appreciated.