Hey guys, I have a 2005 G6 with 152,000 miles. I've been using Valvoline high milage synthetic blend 10w-40 oil. I was wondering if I should keep using that or switch to a synthetic blend or a different weight? I live in NEPA so the temperature has a pretty drastic change from winter to summer and I know the oil weight is based on temperature but I don't know much about it. I have also noticed a slight knock when I first start my car cold but goes away when it warms up. Any help or insight into what oil I should use or anyone else uses with similar conditions would be very helpful and appreciated! Thank You!!