I don't trust manuals, I trust people know what they're doing, and this form seems to be loaded with people who understand this car extremely well, for my 2008 GXP do you guys generally recommend 30 grade oil, or 40 grade? Maybe I'm not using the right words, but I do remember it's 30 or 40. I would think the turbo being a turbo one would go with the 30? If it helps I live in New York, hot summers, cold winters. Would one change the grade of the oil according to the season?