For F250. Runs rough at times and dies while driving down the highway. Not all the time. Oil smells like diesel? At times can smell diesel when we trn off engine. Any ideas?

Sounds like o-rings at the injectors are bad. You are going to have to remove each injector and replace the o-ring. That's the only cause for fuel mixing with oil. Also check your fuel filter carefully to make sure that nothing is blocking the return line, that also causes issues