Ok, since I saw an immediately drop in efficiency and had a good week of data to collect, I didn't feel the need to wait another week to see if there was any difference. I went ahead and changed out the gear oil today from the Nissan Matic S back to the Valvoline ULV. The temperature today was similar to my other test day, no wind, EV was already ambient air temperature for everything, so I did another drive around test going the same exact route I always do so I could compare motor and gear oil temperatures again.
I am convinced that once the motor + electronics hits +140F temperature, the cooling system kicks in by running the radiator fans and coolant pump on high. This adds about a +800W additional power drain to the main battery. 800W is tiny compared to how much power it takes to push the Leaf down the road and for short trips, you won't notice much. Since that's the same difference between running the climate control on or off during the trip, it only makes a small difference on short trips.
First thing I noticed, running +50 MPH down the same route. The ULV is already running the gear oil cooler and the motor is staying well under 140F. The Nissan Matic S can do this but the gear oil temperature remains +20F hotter with Matic S. Also, the Nissan Matic S has a point where if you accelerate/stop enough, for the +50 MPH run, the gear oil heat seems to eventually make it to the motor since it is so much hotter than the motor. It will eventually heat the motor up to +140F and it seems to hold between 140F and 142F, which I guess is the cooling system working to get it down, shuts off, more heat is generated, it kicks back on again, repeat.
On the Interstate at speeds +70 MPH, the Nissan Matic S runs the gear oil at +180F, the motor basically in step with the temperature running +180F also. There is where a big difference between the two oil(s) comes out. The ULV will run the gear oil temperature between 150F to 155F, cooler temperature, sure. But... I never knew what temperature the motor was running at that speed last time. Now I know, the motor is still running *under* 140F. The gear oil temperature is actually higher than the motor temperature now, but steady. The motor temperature holds steady as well. I guess there is enough air cooling plus lower resistance of the gear oil to keep the motor from working as hard and heating up.
I'm still waiting on the results from Blackstone Labs before I make any final assessments of running ULV, but so far, everything seems to point to the direction of the ULV is saving energy and enough of it to make a tangible difference on your range and how hot your motor +electronics + gears system is running as a whole.