15-40W lubes a cold engine sooner upon cold engine start up than 30W or 40W
oil
does.

You can hear the difference.

While that maybe true, in this case we will not be seeing low ambient temps.
And if we were to, we would change the weight of the oil.

"cold" is maybe 80* for engine startup while oil operating temps can be well
over 200*. 15W-40 lubes much quicker at 80* than does 40W.