Because the temperature properties of the oil make it thicker when cold.
When starting an engine when its cold you want 5 weight so the oil flows better, when heated and the oil becomes thinner it attains the properties of 30 weight.
Because the temperature properties of the oil make it thicker when cold.
When starting an engine when its cold you want 5 weight so the oil flows better, when heated and the oil becomes thinner it attains the properties of 30 weight.