Hands Down What Should We Be Using For An Oil All Year Round On The Sti's? Im Currently Using Royal Purple 5w-30 And Oem Filter. Good? Bad? I Live In New England....
Unfortunately, that article has some issues so I would not even think too much about that information. Read the comments here with input from engineers and a tribologist. Dr Haas' Motor Oil University Article.I read all the chapters but I'm not sure how to determine if my 2005 STI in Arizona is @ 10PSI per 1000rpm. All I know is my tuner recommended Shell Rotella 15w 40 due to the hot weather here. But according to this write up, 15w anything is bad due to how thick it is at startup vs other thinner oils. On top of that, Rotella is not synthetic. The previous owner of my car used Amsoil 10w40 in Florida, but Amsoil 0w40 seems to be a better choice. Man my head hurts now... I hear Subarus love Rotella, but i'm not sure where that all started. I know alot of people run it and have very little oil consumption (something that wasn't really covered in this write up). Regardless, I think I'm going back to Amsoil synthetic on my next oil change. I'll even give the 0w30 a shot in this 115 degree summer Arizona heat. I agree with the logic that oil at startup should be as light as possible but still optimum at roughly 212 degrees F. Interesting write up for sure. Now to test some oils.
I live in Saguenay which means COLD winters, moderate summers and limited choices for oil.Again, don't stress about the cold cranking viscosity unless you plan on driving your car to Saskatchewan.
Rotella T6 5W40 gained popularity among many enthusiasts over the past few years because it is a mixed fleet gas/diesel oil that meets API SM specs for gas engines, has a decent amount of ZDDP, and is easy to find.