Of course, it would give better results; its thinner than 10w-30, easy to flow, more heat dissipation, and above all, its the most recommended engine oil grade and No. 1 choice, for most of the vehicles available locally.
Agreed, but the switch may be gradual, and not abrupt, like 5w-30---> 10w-30---> 10w-40.
Why switch to thick oils unnecessarily, when thin ones work fine?