Wal-Mart has the Mobil1 5qt jug for $28 up until just a few weeks ago when they dropped the price to $22/5qt jug. I saw Target had the same deal also, but Wal-Mart has a bigger selection in terms of viscosity/weight to choose from.
I bought the Castrol Syntec 5qt jug for $21.97 at Wal-Mart a couple times when the Mobil1 was still expensive. Yes, I'm aware of the controversy that Syntec isn't fully synthetic except for the European formula.
Yeah, I'm going to pick up a few 6qt cases from Costco also with the $10 coupon. Too bad they don't carry 5W20.
On a slightly off topic note, Wal-Mart occasionally sells Mobil1 oil filters as well for only $10. I just wish that I would've stocked up on them when they were available for sale. I've been getting mine M1 oil filters as part of the 5qt of Mobil1 oil + filter for $30 at Autozone whenever they have the deal (it's been awhile now). They run for about $13 separately nowadays. Where do you guys get your M1 filters and how much?