I've read some posts and I see 0W40 and I've seen 5W30. Which is the best weight to go with? Also which brands are best? My local walmart seems to have better deals. Mobile1 is about $45 for 8qts, Valvolvine Synthetic is about $40 for 8 qts, and Penzoil synthetic is about $38 for 8qts. I ordered my filter from autohausaz.com.