Originally Posted by 2013Versa
I would prefer using 5W-30, as the thinner oil would protect less on start-up.
Actually, it is another way around. The thinner oil protects MORE on start-up. That is why multi-grade oils are used. For example, 5w-30 oil has lower viscosity 5w when cold (on start-up) and 30w at operating temperature after it warms up. It is specially designed to better protect engine on start-up.
The same reason why previously OEMs recommended to use 10w-30 for summer and 5w-30 for winter, for better engine protection on start-up at lower temps. Later when engine tolerances decreased and request for fuel efficiency increased, they started to recommend 5w-30 all year around.