I have always been told to change the oil on your bike after a short ride. Goes for not only the engine but transmission and primary too. Recently, I watched a buddy work on his bike and he did just the opposite. What gives, don't you get a better drain with the fluids warmed up. He felt that you got more oil out since it had all settled in the bottom of the various drain areas. What's the best in this case. Hot or cold fluid drains.