I used to run Mobil1 full synthetic 5W-30
Now I run whatever I can afford, usually cheap budget oils. But I keep it clean. I have been running 5w30 in colder weather and 10w30 in the summer.
I also run a larger filter, #7317, it's about 1/3rd longer and fits just fine. Has the correct valving in it as well. The 6607 is tiny.