I just changed to a synthethic oil i'm using silkolene the oil is red. i've only used "normal" color oil in the past "brown". non synthethic. As the oil wore the color would go twored black when dirty. Now that i'm using synthethic can I go longer before oil changes. Currently i'm going aprox 45-50hrs and does the oil dictate when it is dirty being that it is red does it shade to the black side?