Right or wrongly - in my new (at the time) Hyundai 2017 Sonata 2.4L DI (non - turbo) , I dumped the factory fill at 750 miles and replaced with a syn- blend and ran that 3K miles . After that I have only run synthetic oils (M1, PP , QSUD , etc.) My question is did I do the right thing for this engine with my protocol / process ? ... MInd you Corvettes and other high end sports cars get shipped from the factory with synthetic oil in them , so there goes the theory that I should have used PYB conventional oil for the first 10K miles of the engines life ... *So which camp re you in and why ? Leave the factory fill in and use conventional oil for several thousand miles Or dump the factory fill early and then go to a syn - blend or synthetic oil after that ?