I just bought a 2004 Cat 247 CHEAP, owner used it around farm he said after about 2 hours use left side would start acting up. left track would stop and start. He has been using 303 tractor oil from Carquest. I am thinking the drive motor is going bad and needs rebuilding. But not sure if that oil is too thin and maybe I can get a few more hours out of it ( home use) by going to a thicker oil. Do you guys agree? If so what would be a thicker oil that would work? Live in the South work only in summer. PS machine has about 2100 hrs.