I used to manage an oil and coolant sampling lab for a local Caterpillar dealer. I'm a chemist.
Just to add my 2 cents... Oil is cheap. A new engine is not. As the engine runs, it creates "wear metals or wear particles". That's like adding sand to your oil to be an abrasive. With the wear metals in the oil, components will have a shorter life. This is true, especially in a new vehicle during break-in. I've got under 500 miles on my truck now, but will most likely change oil at 1,000 miles. Then, for me, since I don't plan on putting a lot of Mike's on the vehicle, I'll most likely change oil every 3 to 6 months.
One thing to remember is that time is also the enemy, regardless of miles. Oil can pick up condensate water which can combine with sulfur to create sulfuric acid (sulfation), especially true in diesel engines. There may be trace amounts of sulfur in gasoline depending how pure it is. Regardless of Sulfur, water can cause cavitation erosion in the cylinder walls.
In addition, as oil ages, it picks up oxygen (it oxidizes). This is also corrosive to engine components.
Synthetic oil tempts people to change it less frequently because the oil lasts longer and resists break-doen. You still have wear metals being created when the engine runs as well as oxidation from time with synthetic oil. Changing oil frequently, eliminates these issues.
I don't want to start any debates, I'm just passing along what I taught my customers, and what Caterpillar taught me.
Everyone has their own opinion on oil changes. My view is oil is cheap, a new engine is not. I'm putting low miles on my truck now - saving it for retirement. It will be paid off then. I'll change oil frequently and drive it just enough for now to keep it from deteriorating and enough for me to enjoy this beautiful Longhorn!
Good luck to everyone with their Ram trucks as well!