I am looking into buying an F250 with the 7.3 IDI motor. When i went and looked at it, i noticed the oil pressure when you first started it up(cold) was at 0, but after a minute climbed up just a little below the N on Normal. Is this something i should be worried about? It started up good and there where no weird noises, It also drove good too. What should i do to make sure this engine is working properly? I am new to diesel trucks(this will be my first), by the way.