I just picked up a 2004 LZ23KC604 that has 58 hours on it. Home owner owned and used. I did not get the owner manuals that came with the unit. But I did download the operator and parts manuals from the Ex-mark website. I did not see the Kohler engine manual anywhere. Is it available? From reading on this site (Very good reading I might add) oil changes need to happen around 50 hours. With this unit being two years old, is it to soon to start on synthetic oil? Also, should I go ahead and change the hydro oil and filter? Also, the steering response seems to be just a little jerky. Is this do to the low hours/use or is it just not broken in yet? It just does not seem as smooth as some others I have tried out. Lastly, with the SN# 486484, is it possible to trace back to what dealership sold this unit. There are several in this area. I am extremely pleased this this mower. Its greatest!