We have a Perkins 306(smaller brother to 354)six cyl diesel in a loader tractor that has begun to make engine oil.Diesel is getting in somewhere and I was wondering if anyone has had this happen before?

I 'm suspecting that the fuel pump may be leaking internally  but not keen on pulling it out just yet if it may be another place that diesel can leak in from.Lift pump has been relaced recently.

Engine starts,runs and pulls well,probably takes 30 odd hrs after a oil change to start creeping up stick.

Any thoughts appreciated.

Mike.