Truck Repair: 855 cummins diesel engine, cummins diesel engine, diesel engine

Question
I have an 855 cummins diesel engine on a Versatile farm tractor. The engine is a 1980 year model big cam. The engine is gaining motor oil, which leads me to believe it is actually  diesel getting in the motor oil. How could diesel get into the motor oil on this engine? The engine runs fine with plenty of power but over several hours of running it definately gains motor oil, could this be an injector problem or an injection pump problem?

Answer
Fuel dilution with engine oil can occur as a result of
1. Injector wear (barrel plunger wear)
2. cracked injector cup
3. Cut injector "o" ring
4. wrong injector protrusion due to wrong fixing of injector.
5. Injecion pump shaft oil seal wear.
Check the above or have your injectors checked and replace with new "o" rings.

cheers.