As a self employed auto tech I'm going to try and not make this a "when do I change my oil post ".My wife uses this vehicle and it has 15000km service intervals .I have extended the service plan to 60 000km .Vehicle is currently on 37800kms .Upon checking all fluids and washing the car today ,I was surprised at the almost black like colour of the oil after only 7500kms .The dealer swears they only use synthetic oil on these engines ,however no one at the service reception can say anything further except "Castrol" .My question is ,a grade and distance/time recommendations on this engine from users ? It has the Hyundai k 12 engine .Previous cars of mine have done well enough on 1 year intervals ,each doing 300000kms plus .Same advice I give my clients as most of them do about 10 000km a year .