Hello XXXX,
It is highly likely that by running another round of ARX cleaning and a
rinse, you will be able to stop this rear main seal leak. And yes, it is
crucial that you run conventional oil, for both cleaning and rinsing.
Running a mineral oil based motor oil will help the seal find its old
memory, as well as stiffen the lip on the seal around the rotating crank
journal. It is likely that the high mileage oil would have made the seal
limp.
An aluminum block has nothing to do with a polymer(nitrile) seal and a steel
crankshaft journal. The leak is always associated with the polymer seal
mating with the rotating steel crank. Almost all modern engines are
aluminum.
All pistons are aluminum. There is no truth to Auto-Rx having difficulties
cleaning up aluminum motors.
I think you would benefit from checking or replacing the PCV valve on your
motor. It is a cheap part. The PCV valve allows positive pressure inside the
motor cavity to be released back through the motors intake system. If this
valve is sticky or stuck closed, then the pressure inside the motor works to
force oil out of the weakest seal. This is almost always the rear main.
Rich
