I questioned a Kia Tech on which oil to run since 2007 Kia Sedona V6 and 2011 Kia Forte I4 engines state in the manual: Can run either 5W20 or 5W30 ...preferably 5W30 in hotter climates (Brownsville Texas , Key West , Florida ?) ...So I asked the Kia Tech which one to run and he replied : " For best gas milieage run 5W20 , for max engine life run 5W30" . For sake of arguement, I'm only considering synthetic (QSUD , PP , M1)and would like to get 200K+ miles out of both vehicles with a 7500 mile / 6 month OCI schedule ... Which grade oil would you use or does it matter ?