BAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD idea. Never ever ever use quick fix fluids unless you just want the engine to run another few thousand miles and don't care if it blows up after that, because it seriously might.
If the stuff is sticky enough to find a leak and seal it up, where else is it going to stick and seal up? An oil passage? The oil pump? The oil filter? (HINT: All of those are really really bad places for stuff to get blocked!)
If you have a leaking rear main seal, pull the damn tranny and replace the seal. You might as well also replace the transmission fluid while you're in there; if the car is manual, also replace the clutch, pressure plate, and throwout bearing.
After that, change the engine oil with a good but cheap oil like Castrol GTX. You're going to want to change it after about 2,000 miles because a small amount of the RTV silicone sealant you will use for the rear main seal job will leach into the oil at first. From then on, you can keep using Castrol GTX or switch up to something nicer, like Pennzoil Platinum or Mobil 1. Or, if you really
like your car and/or want to drag your oil changes out as much as possible, get Amsoil.