Okay im sure its been discussed many many many times hear on bobs. But Since I don't have a turbo and I do change my oil at 3,750 miles am I wasting the oils potential to run longer. My car does have a di engine which Hyundai says is hard on the oil. As a matter of fact the tech from Hyundai I talked to said make sure I do change the oil at or under 4000 miles. In the manual it states either 3,750 for severe or 7000 miles for regular use. I do smell gas when I change my oil so im sure there is some fuel dilution going on. I was told its better to run a synthetic with the di engine. I use Quaker State Ultimate Durability 5w30 most of the time and with the fuel rewards on sopus oil then I believe its a no brainer. Why would anyone use conventional oil when the syn oils are so cheap to use as of right now.