For in-store pickup only, Sears offers the Spectrum Plus 128-oz. Car Wash for $2. Even better, Shop Your Way Rewards members earn 20 cents in SYWR points. (Not a member? It's free to join.) Assuming you'll use the credit, that's tied with last month's mention, $4 off, and the lowest price we could find. It features carnuba wax concentrate.
Of note, Shop Your Way Rewards members may be eligible for additional credits and discounts.