Amsoil makes awesome synthetic oil with zinc in it. its pricey but has an extended drain interval. I ran their signature series in my puddle jumper(not their zinc oil)15,000 mi and had it lab tested like they do for fleet trucks. still good ran it for another 3000 mi before changing it. call an Amsoil dealer and tell him your needs(zinc). best oil on the planet and no, I'm not an Amsoil dealer.
