Just my opinion but if I'm correct, the truck is still covered under factory warranty. I wouldn't want to "void" the warranty, or give them a reason to do so. At this point, and for this reason, I recommend the factory recommended change interval, which I believe is 25K mi. Or change it earlier, if you feel it needs it. I wouldn't go longer, maybe it's me being a "worry-wart". :-laf Just my opinion... John