After 1.5 years of various fills using M1 0W20 , 5W30 , QSUD 5W30 and PP 5W20 I have enough synthetic leftovers to do a complete fill for the wife's grocery getter '07 Kia Sedona 3.8L V6 ... Any reason why I can't go with a 6,000 mile / 6 month OCI on this Frankenstein synthetic oil mixture ?