I am aware of the Vastrol Syntek 10W40, however I prefer the 5W for the Chicago winters.
Last year I used Valvoline 10W40 (non-synthetic) during the winter months and discovered that the oil produced a white jell under the oil cap on short trips and the 10W40 sounded like it was a bit too thick when the temperatures got down to the single digits.
Thanks for the input regarding the pricing for synthetic oil that you found. I discovered that Target sells Mobil 1 for $3.00/qt. but I have yet to see Mobil 1 0W40.
1998 Mercedes E320, 200K Miles
2001 Acura 3.2TL, 178K Miles
1992 Chevy Astro, 205K Miles