Not sure if this is a national discount, but at least in the DC area, until 11/26, Advance Auto Parts is having a sale on Castrol GTX at $1.68 a quart, or just a little bit over $20 for a 12-pack case. This is perfect for Castrol GTX worshippers such as yours truly

just a heads up for you DIYers to stock up while it's on sale. Last time they had Castrol on sale I bought a case, this time i'm gonna get myself 2 or 3 cases muahahaha