Please read before starting the seal leak application!

Auto-Rx® Plus is very effective in minimizing or stopping rotary seal leaks.

Rotary seals are found at the front and rear of the crankshaft and cams typically. Many times oil-related deposits can form between the rotating journal of the cam or crank shaft and the polymer seal material. It is critical that the interface between the steel spinning shaft and the much softer polymer seal lip stay clean.

Not only does the motor oil lubricate the seal interface it keeps the interface cool. Staying on top of maintenance is the best practice. Nobody wants a 4-figure labor bill to replace a $25 dollar seal. If you do have a rotary seal leak, running Auto-Rx Plus can solve or greatly inhibit the leak by cleaning up the seal and rotating shaft. No motor oil contributes to a rotary seal leak, contaminants do.

Another very helpful hint is to service the crankcase breathing system. In most cases that is replacing the simple PCV valve on most motors. A sticky or under-performing ventilation system will trap positive pressure inside of the crankcase. And as a result oil will get forced out of the motor at the weakest point. Many times this is a rotary seal.

The application is quite simple. First, add a single bottle of Auto-Rx® Plus to a fresh oil fill. Then drive for 3000 miles. Many times the leak will stop during this segment. Then change out the oil and refill with a fresh oil and run another 3000 mile interval. Provided that the leaking seal is not cracked or severely worn, the leak will stop or be greatly diminished. Even if the seal is beyond help, cleaning up the affected area of the motor is a good thing. Why spend the big bucks replacing the seal and having it installed in a dirty system?

Finally, don’t confuse a rotary seal leak with a gasket. A gasket leak is due to cracking typically and can only be solved by replacement. Gaskets are typically found at the valve covers, oil pan, intake manifold and cylinder heads. Auto-Rx® Plus will not solve gasket leaks.



Add 2 bottles of Auto-Rx® Plus to a fresh oil and filter. If you have a very recent, low-mileage oil change using ONLY conventional oil, you may use your existing oil.


After adding Auto-Rx® Plus, run the motor for 5 minutes to disperse it into the host motor oil.


Over time, drive at least 2,000 miles with normal driving habits to allow the Auto-Rx® Plus to gently cleanse the oiling system internals, including seals (a longer interval of up to 4,000 miles is fine).


Drain the oil, change the filter, and refill with conventional oil (Group II only).



RINSE PHASE: Drive the vehicle normally for 2,000-3,000 miles; then change the oil and filter again with nothing added. THE LEAK SHOULD STOP DURING THIS PHASE WITHIN A FEW HUNDRED MILES.


Congratulations! Your cleaning application is finished when the leak stops.

WARNING: Returning to Group IV synthetic, semi-synthetic, or high-mileage oil may cause the leak to return.


Vehicles with over 100,000 miles may require a second application. Repeat Steps 1 through 6.

How It Works

In solving a rotary oil seal leak with Auto-Rx® Plus, it is important to use conventional motor oil and not full synthetic motor oils. Conventional motor oils have a mineral oil base. This tends to stiffen the seal material a bit, as opposed to synthetics that tend to keep them very pliable. Rear main seals typically weep or leak from a build up of oil contamination that builds up on the end of the steel crankshaft, right where the polymer rear main seal interacts. So some junk gets caught up at the sealing lip. The shaft is no longer perfectly round as it is spinning. By allowing Auto-Rx® Plus to clean the crankshaft and seal material, it has a good chance of finding its old polymer memory and perform once again. We cannot stress enough how important it is to run a mineral oil-based motor oil to enable the polymer seal to find its original shape and stiffness. It is a very labor intensive proposition to change out the rear main oil seal. The transmission has to come out, etc., and this is very expensive.