I just happen to have the Chevron Salesfax digest here . The pour point for the Delo 400 15- 40 is listed at -29 C. You seem to want to compare the Delo to the Rosmella, but I just installed the Delo 400 Synthetic in 5- 40 at least for the winter. It has a pour point of -60C. I have not decided on change intraval, however I know that I will keep my filter change on the same as the old change intraval and put that 12th quart to good use.
2003, 2500, 6sp., 4.10LS, Laramie, Rhino liner, B & W Turnover Ball, Jacobs exhaust brake, sirius, Truxedo bed cover, Schuck Cushion Hitch, Mag-Hytec Rear cover