Hi, I'm new to the forum, I just purchased a 05 WRX, and I just had a simple question. I'm going to chance the oil, and the cap calls for 5-W30, but also mentions checking the owner's manual. I didn't get a manual when I purchased the car. Some of the German cars I've owned require different viscosities at different times of the year. Can someone with a manual tell me if Subaru recommends a heavier oil in the summer? (I live in WV, and it rarely exceeds a 100 degrees here.) Thanks in advance.