PTT Fully Synthetic 5/40 ZIC xq 5/40 & Valvoline 5/40 belongs to group 3 or 4? Kixx 5/40 PAO is confirmed group 4. But I've read their bottles thoroughly, but its not mentioned over there. And asking such questions to their company dealers is far beyond their level of comprehension. So how to know it?
And also, how to know that engine needs x group synthetic oils only? I wish OEM should have it mention in the manuals.