Yuk, hows this; if you have a leak on your car engine, trans, diffy, etc. Fix the leak. Sometimes as Mola mentioned you have to go back and retorque.
If you add ANY fluids to those components and they leak afterwards, still fix the leak.
Kev, you need to check the torque and ensure a good seal on the pan gasket.
Any oil with a good ester component synthetic/natural has a tendency to find loose spots or clean the dirt and build up that was holding the lube in place.
Fix mechanical issues first. Auto-Rx isn't magic it is a cleaner and secondly a lubricant.
If dirt is restricting a good seal on a polymer seal that can be rejuvinated then RX may help you, if its a crushed gasket for non moving components I doubt it will help unless they are polymer and dried out.
No one is protecting RX from criticism. Its a chemical tool, has to be used right by people who understand what it can do and what limitations it has.
Terry