So I've had the rear wheel off my sons bike for a day or so while we give it some tlc and I've noticed that in the morning it looks like the wheel bearings have seeped a little bit of oil. They are sealed bearings...is this normal? I thought bearings were packed with grease, not oil? It's about half a drop of oil. I kinda just want to ignore it and hope for the best because I don't want to take the chance of ruining the seal when I try to take it off. But I'm also kind of anal and don't want to let it go if I really should fix it. I'm going to take him riding for the first time on Saturday and I don't want to do anything dumb that'll delay the trip! Thanks for the input...