My truck is not broke in yet and living in Missouri it doesn't get cold enough to need a synthetic IMHO, so I don't run synthetic. My local Walmart really likes to play the price game. Rottella Synthetic used to be 18. 88, then they dropped it to 12 something for a few months, and then jacked it up to 18. 88 again. Now its 12 something again.
A lot of stores also have items called price leaders they sell. Sometimes they sell something under cost to get you in the store. But they figure you will buy some other stuff which is not marked down, so they still make a profit. KL