In Toyota FAQ page, one question is asked, "Can I use any brand of 0W-20 synthetic oil?" To which there answer is, "Genuine Toyota motor oil 0W-20 utilizes a Toyota-specific additive package that will provide the best results for oil performance and fuel economy. However, other 0W-20 synthetic oils can be used as long as they are ILSAC certified, which is found on the oil container label." What makes Toyota so different that they have a Toyota-specific additive package? Why couldn't other oils being as good or better? In my owners manual, they do say ILSAC GF-5 oil can be used. According to that, I could use Pennzoil Gold which is a synthetic blend. If Toyota want me to use a synthetic oil, why don't they use some specs to eliminate the use of Pennzoil Gold?