No point going any lower than what manufacturers calls for.
Nor is there any point in going higher.
Oil viscosity is heat dependent. Manage oil temperatures effectively, and a thinner grade oil works fine. Let oil temperatures get too hot, and a thicker oil will be needed.
0w16 oil is about 7.2 cSt at 100*c., and 8.7 cSt at 90*C.
And, for example, M1 5w20 is about 8.9 cSt at 100*C. But at 90*C, it is about 11.0 cSt. However, at 110*C, viscosity drops to about 7.3 cSt., and at 120*C viscosity is getting low at 6.1 cSt.
M1 5w30 at 100*C is about 11.0 cSt, the same as the 5w20 is at 90*c. At 110*C viscosity falls to 9.0 cSt.
And, M1 5W40 FM is at about 8.9 cSt at 120*C, the same as the 5w20 is at 100*C.
So, one can see that all the viscosity grades overlap, depending on temperature.
A 16 grade at 90*C is about the same as a 20 grade at 100*C, which is about the same as a 30 grade at 110*C, or a 40 grade at 120*C