That's a problem I've been praying I wouldn't have to figure out on our last 2 big trips. Especially on those 2-3 hours stretches where there are no service stations or cell phone service.
I almost did have a major problem last year when we were 1000 miles from home and I found a huge puddle of oil under the truck, on a Saturday. Thought my pan was cracked and we'd have to spend 4 days waiting around for the part and fix, although it wouldn't have been terrible since we were just outside of New Orleans. Turns out it was just a lose oil filter. BIG alleluia on that discovery! Plus the dealer I limped it to only charged me for 2 quarts of oil and had us in-out in 30 minutes. They would have my biz for life if they were local.