I have been using MOBIL1 10w30 with supersyn technology motor oil since I had about 50 hours on my exmark mower with the 20 horse kohler engine, am I wrong by having done this? Have I caused any damagw? I was reading on the Exmark site that they recomend that you not switch to synthetic until 250 hours. I am getting concerned about this, who else has been using synthetic oil? Can someone ease my mind???