I have a gravely hd52 that i am going to do my first hydro oil change on. The filter # is 21545100 . does anyone know a cross reference filter that will fit it from an auto store. I usually use wix filters but cant get a cross reference. also it says use 20w50 motor oil with an sl api classification. Not quite sure what that means. I use rotella oil in all my motors, would that work?