For a synth blend, you cant beat one of the conoco-phillips variants. You can often find 5w30 or 10w30 for less than $1/qt after rebates. Regular price near me is ~$1.79/qt. I was just at my local autozone the other day. The LEAST expensive motor oil they had on the shelves was coastal for $1.79qt. I wound up paying $1.99/qt for 5w-20 exxon superflo for my 2001 windstar!
Joel