Also, you need to be sure to seal all of the end grain (top and bottom) of the door with the finish you choose. Otherwise it will warp badly. Also you might want to also coat any holes you drill in the door for strike bolts and door hardware before you install the hardware. This is because Oak has the tendancy to turn black after getting wet and eventually some water or condensation will creep in there and start turning the area black. If your door is a true raised panel then you also need to keep an eye on the shrinking and swelling of the panels where they meet the rails and stiles. Season to season they will move and crack the finish and water might get in there too.