I finally got the results from a longer run with Mobil 1 EP 5W-30. I did change the filter at 6000 miles but didn't need to add any more oil. Results were very good but not quite as good as the Magnatec on a shorter run. Plus, my mpg seemed to be dropping considerably towards the end. I think I'll stick with Magnatec and ~8000 miles.
The Leaf is doing great. All battery bars remain at 31,000 miles but we had to replace the lead-acid accessory battery. I've also become aware that I should change the brake fluid soon.