Hey Terri...I have the lazer Z 60 with the 25hp Kohler on it. With 700 hours on it, the motor gave up..I had the exhaust valve an head gasket go on it. I took it to the dealer. He replaced the valve, an gasket. 2 weeks later the same thing. It has also developed an awesome oil leak from the base (gasket!!!) Why is there no gasket for this? Dealer just puts permatex on it an calls it good. Says Kohler doesn't't make a gasket for the base...??? Dealer fixed it again. While he was inside the head he found it cracked..The head was ordered an replaced. So was the burnt valve for the second time.Permatex, or gasket sealer whatever they used to fix the oil leak. 2 Weeks later blow the other head in the middle of my biggest yard. Take it back to the dealer. He has to replace a burnt valve, and the head on the opposite side. Kohler now comes to the conclusion that all these problems are the result of using cheap gas. The dealer concurs with Kohler, and explains that Kohler is not going to honor their warranty now because I have been using cheap gas... I dont know about you, but I have personally seen the price of gas...It aint cheap. I also referred to the manual. It tells me 87 octane or higher. I use 87 octane.. In the mower, my vehicles, pretty much everything. The only problem I have had is with the Kohler engine. If Kohler doesn't't want us using less than 89 octane, this is something that should be stated in the manual. It is not. I really dont like the fact that Kohler wants to cop out on the warranty because I have been using 87 octane, which has been gumming up the valves an causing them to stick..... I can tell you this.....It has cost me alot more than Kohler has paid in down time!!!