Switch to 5w-40 still have hard cold start

I made the switch to the 5-40 rotella after years of hard cold starts under 30F degrees. Battery's, GP's, starter,GP relay all check out ok, and actually have been replaced not long ago (All within 1-3yrs or so). It cranks over a ton better but lopes or romps a few times and won't keep running. On about the third try I crank and push the gas pedal down a little and it keeps running (roughly) and finally will take off. It's almost like the oil to the injectors isn't being sustained enough at first. Or the injectors are just in too bad of shape. It really is no different than with the 15-40, almost worse. Maybe low press oil pump or HPOP? Or maybe even batteries gettin wore out? Voltage looks ok.

Any other thoughts out there?

This was not plugged in and got to about 10F degrees last night.