Engine lube oil + transmission fluid?

Synopsis: General mention on a possible engine oil seal leaking on car. Another individual emphatically stated that adding a small amount of transmission fluid to the engine oil would cause the seal to swell and stop the leak. He further swore that he had done this on his old Ford pick up & it worked like a champ. No more engine leaks. I stated that this was not a good idea and would never recommend anyone trying this as the two fluids are designed for two completely different useages. (chemical make up and all that jazz)

OK, before I get all of the ranting and raving about not putting a certain type of fluid where it was never intended to go, let me assure you that I never have and never intend to do such a thing. However, as I have never heard of such a thing, my curiosity has gotten the best of me.

Has anyone ever heard of or even tried doing this? If so, what were the results?

I have seen people add transmission fluid to the crankcase. The amount was usually a pint or so. The people who did it claimed that it would quiet noisy lifters. I’m not certain that it had much benefit, but it probably did no harm. I suppose that the transmisssion fluid may have an additive that keeps the seals in the transmisison pliant and might do some good in the case of a leaking seal.

I’ve never thought it was a good idea and agree with you that different lubricants have different purposes. I do remember a student when I was in college that had a 1950 Pontiac and a connecting rod bearing began knocking when he was 50 miles away from campus. A service station drained the oil and filled the crankcase with 90 weight gear lubricant for standard transmissions. He made it back, but that was the end of the Pontiac.