That brings up the multi-viscosity oil discussion for driving, not storing, during the winter. Should we use 5w30 or 5w40 year round?
I use 15W40 in my diesel year round and rarely have any issues with starting. Of course, the starter may have as much horsepower as a stovebolt 6.
The only reason that you'd use a 5W-anything is for starting issues, and I doubt a stovebolt (or any gas engine) would have issues in Illinois temperatures.
