Is it bad when oil gets into the throttle body?
Yes. Oil in throttle body passages can cause idling problems. It also restricts flow through the intake, reducing power. Where does this oil come from? Modern engines have a Positive Crankcase Ventilation (PCV) system. All engines have a certain amount of “blow by.” The pistons don’t seal perfectly, so some of the air and fuel gets past them and goes into the crankcase. The PCV system sends these gases back to the intake. Along the way, they can draw oil through the system. Most issues with oil entering the intake are caused by a failing PCV valve.