i can say that i us rotella t6 in most my stuff but it is not cheap. some stuff only gets t4. any new oil will be better then the old oil in the engine. hence why i said new. and with a engine that holds like 3 liters and revs for extended periods over 5000 rpm i like to change it often. but then again i use my truck as a work truck in the woods.
i just get the 20L pail of plain 10w-30 from Wal-Mart and use zinc additive with it while changing the oil. cam seal leaks are an issue on these so i never use synthetic oil.