I would not waste good synthetic oil on an engine driven this little. I would use any name brand dino, and change the oil at 6 month intervals. IMHO, if you are not going to use synthetic to go to extended oil change intervals, you are wasting your money. Ordinary dinos will get you at least 200,000 to 300,000 miles if you change oil at 3000 to 5000 mile intervals.
I, personally, used M1 from the time it came out in the 70's to 2001, when I retired. I always did a one year OCI, which usually amounted to 18,000 to 20,000 miles. Never a lubrication problem, and my engines always remained quiet up to 140,000 miles. I never put more miles than this on my vehicles; I was usually ready for something new after 5 or 6 years.
Since I have been retired, my yearly mileage is now about 6,000, and I use name brand dino, changed at 6 month intervals. Can't see wasting good synthetic by using a one year OCI when that would only be 6000 miles.