If you want to start a long discussion ask about what type of oil auto technicians prefer. The only thing that would bring up more discourse would be blond, brunette or redhead.
Every mechanic, technician or grease monkey, wonder how that name came to be, everyone will have a different preferred oil.
There are many different ones on the market, synthetic, semi synthetic and plain old oil. Also weights SAE 0-40, 10-40, 10-30 5-30 and of course straight grades 10 to 60. Many manufactures also have their own oil GM has a synthetic they almost demand using.
Years ago I worked on NP railroad trucks and cars and they used 10 weight year round and got mileage into the 100K out of their engines, now days 200K is not unusual.
Most techs would say to stay away from semi synthetic oils as they are only a small percentage of synthetic. I think most would choose synthetic, of course the brands would vary with the edge going to Mobil 1.I am sure most GM Techs would choose their new oil and they are correct. However sticking with the same oil is also important if you have a vehicle with some miles do not switch to synthetic as it could cause problems such as leaks and oil consumption.
The weight is usually determined by the vehicle manufactures recommendations. Many use 5-30 so the upper cylinder gets adequate lubrication.
Extended mileage is also a good choice for high mileage engine, I use this in my sunbird with 136K, I use Mobil in my LeBaron and Mobil 1 in my other 2 cars 5-30 in the Pontiac and 5-30 in the winter and 10-30 in the summer in my Dodge pickup. If I had a new GM I would use their new oil also I have considered switching from Mobil 1 as they have apparently changed there formula, but I don’t what I would switch to.