Wife's '07 Kia Sedona 3.8L DOHC (still under warranty): This vehicle was used by wife and kids now just the wife drives it as a short tripper , running local errands , etc. with little interstate / highway mileage . Kia manual recommends 3750 (extreme) or 7500 (normal) mileage for OCI's . I was running synthetic for 6000 / 6 months before and it always hit 6000 miles before 6 months . Now the vehicle is not driven as much - should I drop back to a 5000 mile / 5 month OCI with synthetic (PP , QSUD , M1) for this short tripper or can I go longer ? * The only thing I will add (if it helps) is this engine has a timing chain - as for wife , she has more of a lead foot than most people I know ...once the engine is started she is off to the races !