My plan was to do my first oil change around 2500 miles with Valvoline 5W-20, wait until 5000 miles and then start using Mobil 1 Synthetic 5W-20, and then change it every 5000 miles thereafter. I have a few very strong refrigerator magnets stuck to the oil pan near the drain plug to help keep the filter somewhat cleaner, I'll just pull them off when I drain it out and put them back when done. I just recently found out this motor has an 8 quart oil pan, I'd imagine it would take a while for that amount of oil to get pretty contaminated.
@WTD, I'm a railroader as well as your fiancée's son, so I know the lifestyle. Going on 19 years now with 18 to go. I did a lot of driving early in my career too, but luckily I live 5 minutes from the yard where I work now.