[Jakey]

There is this thing called gravity. You see, when you turn off your car, the combination of your oil pump ceasing activity and the fact that oil is a fluid leads to the oil draining back into your oil pan. So, the odds of oil leaking out around the valve cover with the engine off are pretty slim. What may be a good idea would be for you to start your car after cleaning around the base of the valve cover and then looking for leaks from cracks or blown gasket(s).