The rear main seal of an engine is often mechanically difficult and time consuming to get to, making its replacement very costly in labor charges. This makes a liquid rear main seal repair an appealing option.
Bar's Leaks makes a Rear Main Seal Repair motor oil additive which, in addition to treating the rear crankshaft seal, it also treats other rubber seals the oil comes in contact with.
The product was originally made available in a silver quart container, but is now also available in a smaller bottle as a triple concentrated formula, seen at the left. In both cases it is a slightly-thicker-than-water golden brown fluid which appears similar to new oil.