Any cross contamination by ethylene glycol (green) and long life (purple) will cause ineffiecency of heat transfer or cause coolant protection loss and overheating. In the engine dyno labs when automobile companies switched over to long life we had to flush the systems with water and TSP (Tri Sodium Phospate) to scrub reminants of coolant out before refilling with long life. Purple will not hurt green as much as green will damage purple. It will destroy aluminum radiators rapidly depositing the chemicals on the iron block. I do not know if Kubota uses copper or aluminum radiators but I would stick to manufacture reccomend because they run so darn hot freeze protection is not as compramised.