Any leak from a car's oil seals shows the seal is bad or going bad. Denying that your car has a problem will only endanger your car's engine, not to mention waste oil that leaks out. Some of the causes of rear oil seal leaks include age, driving with too little oil in the engine, and from extended car storage. There are a couple of ways to temporarily stop a rear oil seal leak, but the best fix is still replacing the seal.
Use 50 weight oil to temporarily stop the rear oil seal leak. The 50 weight oil will slow down and seal the leak of the seal between the crankshaft and the seal. This oil is thicker and heavier than regular engine oil, so will slow the leak.
Use a specifically made rear main seal repair fluid that can be bought at an auto parts store. One such product is Bar's Leaks Rear Main Seal Repair Fluid. Pour the fluid into the crankcase as if you were adding oil. This slows the rear seal leak, but only temporarily solves the problem.
Check your car's positive crankcase ventilation (PCV) valve. If the valve is clogged, it needs to be replaced. A clogged valve causes combustion gases to build up in the engine and may weaken the rear oil seal, leading to a leak.
Replace the rear engine seal. This is the only means of permanently fixing the problem. Contact a mechanic to change the rear engine seal, as replacing it is time-consuming and difficult, since the fix involves moving the transmission and disassembling the engine to get at the crankshaft to replace the seal. As a car ages, the rubber in the seal hardens and cracks, and eventually the real oil seal must be replaced.