I too am second guessing myself. The Elantra calls for a 7500 mile OCI for normal use with an API SM GF4 oil. 5w20 is recommended, but it can use a 5w30 or a 10w30 if needed. Would this be a safe OCI with a dino or should this be left to a quality synthetic? The car sees mostly highway miles.. about 20,000 a year or so.