The s40 takes about 2.1 quarts. you will want to use an oil that is made for motorcycles, you can get it at most auto parts stores. get 10w-40 .Oil filter is under a triangle shaped cover on the right side of engine with 3 socket cap bolts holding it on. Make sure that the o ring in cover plate stays in place when reinstalling. the oil drain plug is on the left side lower engine case some were below and near the foot peg. Hope this helps Jeff.