SDblitz858
New member
Heyfam, please remove if it does not belong here and yes I have done my researchbut I am still confused to weather go by what the manual says or go by what isthe best for this engine. Again, I have a completely stock 2018 Subaru Sti,21000 Miles right now and all I have put is Subaru OEM 5w30 oil and lastchanged 19kmiles with AMSOIL signature series 5W30. For warranty purposes(found our later on its not even API certified for warranty use only XL series)I am in San Diego CA and thru word of mouth around me and research that If I wantthe longevity of my engine and keep bearings happy I have to use a 5W40 oil. PreferablyMotul Xcess 5w40 on a stock engine.Can someone please enlighten me if I can useMotul Xcess 5w40 on a stock engine to prolong its life? Or do I have to bemodded at the very least to use that oil? Also heard its not suggested if youhave a stock cat. Now im lost again since most are suggesting it for a stockSti but not with stock cat? Any response is gladly appreciated. Also, I Daily the car and occasional mountain runs.