I am in the camp that in a GDI engine that using synthetic 10W30 oil with it's lower NOACK and lower VII's content would be best for a GDI engine (in terms of reducing intake valve depositis) ? Conversely , recent updated tech information may prove such a belief may be a myth and no longer valid : 1) Updated information suggests a lower NOACK oil is not a significant contributor to GDI intake valve deposits . 2) High amounts of VII's are a contributor to intake valve deposits , HOWEVER newer formula VII's are of a composition now to where that is not as much of an issue as with previous earlier SN rated oils and before . Better oil formulas (better base stocks , improved VII's etc.) in SP rated oils suggest that using a good SP rated synthetic D1 / Gen 3 5W30 oil may be best in a GDI engine where both 10W30 and 5W30 were previously recommended in the owner's manual . Lastly , in GDI engines which do not also inclide dual GDI / PFI injectors - it would still be a good practice to runa intaake valve cleaner (i.e. CRC) every 10K miles (or every other OCI along with top tier gas for optimum engine performance ... More capable folks here such as Gokhan , Molekule , etc. can weigh in on key performance indicators for oil / GDI engines I allude to in this post .