I use Valvoline blue 15-40. Fired her up this morning in -37 C and oil pressure jumps right up to normal, no delay at all.

 

Shoot... I'm running Exxon XD-3 15W-40 and been down to -16*F this winter and starts easy every morning... Only 1 cycle on the grid heaters...

The rest of the time its plugged in the garage staying warm. Then I don't even wait for the light I just hit the key and I'm gone...