[Dwight Southerland]

Not exactly true for GM cars. Corporate policy for many years was to design the oil pan to hold a quart more than the minimum required for maximum operation, thus the "1 qt low" mark on the dip stick was really still okay for all modes of operation. Their recommendation to keep the level up was to maintain that cushion.

Maybe other mfrs were different, but it would not make sense to design an engine with an oiling system that could nominally run below the minimum necessary to maintain engine longevity and then place a 50K to 100K mile warranty on it.