Yes, just make sure it is a diesel rated oil. There are varying opinions on how long you should wait for the engine to break in first. 10,000 or 15,000 miles is probably safe. 5w40 is the commonly used synthetic diesel oil.
synthetic to conventional - ok conventional to synthetic - no
Yes, and you can even mix them together.
yes it is fine but of course synthetic is the best to use if you can. Double check your oil requirements with your owner's manual. If it states that normal oil is okay, then go ahead. If your owner's manual dictates Synthetics, then DO NOT switch.
Yes
The 5.9L holds about 11.5 to 12 quarts
The stop engine light might not come on on your N14 Cummins when the switch is off.
It's okay to use Synthetic oil on any vehicle but bare in mind, if your vehicle has previously run on regular oil you will need to drain all the oil out completely in order to switch to synthetic, once you run on synthetic oil though you have to keep the oil synthetic because switching between different types of oil will really mess up your vehicle.
yes
It won't take. Synthetic hair is made from acrylic or plastic.
Yes, you can not only switch you can mix synthetic with conventional oil.
i'd say its better. you might get leaks, because regular oil has bigger molecules than symthetic. i run synthetic in my truck with 193,000 miles all the time no trouble
Yes you can. Contrary to a popular belief it does not hurt to switch between or mix synthetic and conventional oils.