For those who are interested in this kind of stuff. . . It went down to 21F last night (probably much lower than that with the windchill factor) and the car started right up with no problems. No tapping or clatter. By the way, I know that the Delo has a pour point of -39F. Anybody know what this Caltex Delo 400 15W-40 is? Is it the same as the regular Delo 400? The spec sheet says it's the fist oil to meet the Global DHD-1 specification. I'm not familiar with DHD-1.