Why are you doing this? Now you have an oil much thicker than Nissan spec'ed for the car.
A lot of people just don't understand oil, viscosity, etc. and have been brainwashed by those big numbers on the front of the bottle that don't mean a damn thing about viscosity of that oil slinging around in an engine.
This is your Amsoil 0-30's viscosity:
Kinematic Viscosity @ 100°C, cSt (ASTM D445) 10.3
Kinematic Viscosity @ 40°C, cSt (ASTM D445) 56.56
AMSOIL - Signature Series 0W-30 100% Synthetic Motor Oil (SSO)
This is your Amsoil 5-40's viscosity:
Kinematic Viscosity @ 100°C, cSt (ASTM D-445) 13.7
Kinematic Viscosity @ 40°C, cSt (ASTM D-445) 79.7
AMSOIL - European 100% Synthetic 5W-40 Motor Oil (AFL)
This is the Nissan Ester Oil that is so highly recommended by Nissan:
MyG37 - View Single Post - Blackstone Laboratories Oil Analysis Reports
I could not find industry spec on this oil, so I found a sample with 2K miles on it sent to Blackstone Labs. The cSt at 100*C was only 8.19. So either Nissan's Ester oil (which is just conventional base-stock with an Ester addative--nowhere near as good as your Amsoil) is VERY VERY thin, or it shears down VERY VERY FAST, but considering that at 5K miles you can see that his sample sent in was 8.38, I don't think it is having an issue with shearing. IT appears to have thickened up a bit, for what reason I do not have an answer, but that is not completely uncommon.
Either way, you took a 10.3cSt oil and added a 13.7 cSt oil. When an 8.X cSt oil was spec'ed
WHY!?