I would mow the lawn then lift it up and use the drain plug (100% there is one.) and let it all drain out. While down there I would check the blade. If it has been a season since it was sharpended it is worth having it done (also have them check the balance and see if it needs to be replaced.) then add the 20oz of either 30w or 5w-30 (I use supertech, works great) and enjoy!