PJ - This will be my first oil change and I think the previous owner was using "Opti-4"..? This was done through the Hustler Dealer. The paperwork says this oil doubled the engine warranty. Do you know anything about this oil?. I'm not sure if it is Synthetic or Conventional. If I just use regular Brand Name oil do you suggest Synthetic or Conventional? What about which Brand? Also, do different oil filters make any difference? Sorry for the high amount of questions. This is my 2nd Hustler and I just want to make the right decision.