I have a Kubota 4030SU. Recently, while changing antifreeze, I noticed in the book where it stated to use only permanent type antifreeze and specifically stated not to use the semi-permanent type. What is the difference? I refilled it with Prestone. Is Prestone adequate for this application? The engine appears to run at the same temperature as before. I'm concerned with preventing/minimizing cavitation. Will Prestone be suitable for cavitation prevention if changed annually? I've only owned the tractor for a year and I assume that it has been changed as scheduled during its life. Is it advisable to add a conditioner to the antifreeze?(Like the conditioner that is recommended for Ford Powerstroke cooloing systems to prevent cavitation)