I noticed nobody has replied yet. This must be a new tractor to you! I would advise you to get yourself an operators manual and use what is recomended. Whey you ask what kind do you mean brand or specific type. Every vendor has an oil that meets specifications, they just call them different names. Most Tractors use a TDH (transmission differentioal hydraulic oil) or UTHF (Universal transmission hydraulic fluid). With these "generic" names you can go to any vendor and they will be able to assist you. But like i said get yourself a manual so that you ensure that yoy use the oil with the proper specifiactions. Also if this is a new tractor ask the previous owner so that you may use the same brand of oil.