Im sure this is a overly asked question on these forums but what oil is best for the tuff torq k46? I'm replacing the fan (no blades on it, and origional problem to tranny.) But i also wanted to change fluid while its out (I dont have the money to upgrade to the 66 as recommended.) I saw either the j20c or 10w30 in this chart, and have also read people suggesting 5w50 synthetic oil. Trying not to spend $10 a quart on synthetic or $16 a gallon at John deere. Suggestions??