5W40 is OK with our engines per the user manual
0W40 is basically less viscous at cold start. Manual states:
From -35F to 100F use 5W30
0F to 120F 10W-30 or 10W-40
We get triple-digit temps here sometimes.
Why 40 instead of 30? Because it seems that per my last UOA the Mobil 1 5W30 still allowed some higher than average wear [had higher readings of iron, amongst others]