Hi. I would like to hear both the "official" exmark recommendation, and also what oil other owners use in their exmarks. Between my brother, myself , and a guy at work we have 3 exmark HP's. Mine is a 23hp Koeller, my brother's is a 17hp Kaw, and my buddy's is a 23hp Kaw. Mind you these exmarks are mainly residential, (at lease 2 of them), so they will only have about 45 hours per year on them. Two are brand new, still having the "break in" oil in them with less than 5 hours on them, now ready for their first oil change. We are thinking of using a synthetic oil, like AMSoil, or equivilant. The exmark manuals do not seem to advise that much...it just says "any 10-30 oil" for only summer use. After upgrading to something as nice and expensive as an eXmark...I want to baby it with the best. Thank you all in advance for your help and advise.