I am a auto mechanic by trade and I am begining to start my own lawn care business. Being in Florida with the high heat and tough grass, I use a straight 40 wt. due to sand and dust and sever service every 50 hrs filter and oil . I have a Grasshopper 614 18 hp b/s and a exmark 25 hp kohler. I was told by many shops about amsoil synthetic oil and bypass filter kits for my exmark but the cost of $250 for this oil filter kit seems high. The oil wether it is conventional or synthetic is only good until the saturation point is reached and the life of the oil is then over. The only way to know this is to have the oil analyzed. Other l/c owners say they go 150 hours with amsoil and bypass filter kits I think a conventional oil and filter changed before saturation would be equivelent. The manufacturer of the engines researched and analyzed the oil and amount of time between changes. My question is With the cost of down time and repairs are there any advantages of using synthetic or conventional oil????? I was told amsoil doesn't remove heat from air cooled engines. Is this true? Thanks for any imput.