Home Depot is having a storewide clearance sale (I think until the end of July). Anyway, Pennzoil Platinum Synthetic Oil is on sale for $2.60 a quart. Now the deal is that there is a $15 rebate when you purchase 6 quarts (case). This brings the cost to about $0.10 a quart plus tax, envelope, stamp, and time to fill in the rebate.
PP is an excellent oil. I found 10W-30 in stock, as well as 10W-40. Other Pennzoil oils such as high mileage were also on clearance, but there is no rebate on these.
The rebate is for a MasterCard Gift card, which you could use to buy gas, groceries, etc.
Sorry, the file is too big to upload. So here is a link.