Oil in reservoir bottle

Yesterday my granddaughter came to borrow my 500X2 to go hog hunting and I did a check of everything and found a little oil in it. Popped the rad cap off but nothing in it. Checked the oil and still at same level and no water in it. Is this the making of a gasket going bad and time to get new ones put on. I guess after 11500 miles it is time for something to happen. I told her to be and sure and keep an eye on it and if anything happens park it.

Ronnie