Rear main seal leak on 1996 Tahoe 5.7

[Atrain1]

I don't know of an additive, but if you are using synthetic oil it can make a car leak oil because it is so much more "slipery" than regular oil.

I have never used synthetic oil do to it being thinner thin conv oil. I dont even use it in my race Engines. I had a 1978 Grand Prix that would sling oil out of the timing cover all over the passenger side of the engine compartment, I used an additive and it stopped that very large leak. Now the the problem is I can not remember what I used.