I checked the oil. It does not appear to be thinned out with fuel. It does seem that I have had to add oil to the engine more than I would expect to have to. I filled it, ran it about 30 - 40 hours, and now the oil level seems a little low. I think I also have a small leak somewhere since I see some oil seepage under the engine. Not too bad though. Probably the oil pan.
Have a diesel mechanic coming this week. I'll repost to this thread.