Does it matter what type of oil you put in a 2001 yamaha blaster crankcase?? if so, what's the difference?

does it matter what type of oil you put in a 2001 yamaha blaster crankcase?? if so, what's the difference? i have looked at a couple forums and i have seen regular engine oil- 10w-30, and in others i have seen gear oil... let's try to be specific please... if it doesn't matter, let me know! but i'm sure there is a difference!